thodg/libgit2

diff --git a/include/git2.h b/include/git2.h
index f39d7fb..2961cc3 100644
--- a/include/git2.h
+++ b/include/git2.h
@@ -26,6 +26,7 @@
 #include "git2/deprecated.h"
 #include "git2/describe.h"
 #include "git2/diff.h"
+#include "git2/email.h"
 #include "git2/errors.h"
 #include "git2/filter.h"
 #include "git2/global.h"
diff --git a/include/git2/deprecated.h b/include/git2/deprecated.h
index a2b117f..6b268eb 100644
--- a/include/git2/deprecated.h
+++ b/include/git2/deprecated.h
@@ -294,6 +294,102 @@ typedef git_configmap git_cvar_map;
 
 /**@}*/
 
+/** @name Deprecated Diff Functions and Constants
+ *
+ * These functions and enumeration values are retained for backward
+ * compatibility.  The newer versions of these functions and values
+ * should be preferred in all new code.
+ *
+ * There is no plan to remove these backward compatibility values at
+ * this time.
+ */
+/**@{*/
+
+/**
+ * Formatting options for diff e-mail generation
+ */
+typedef enum {
+	/** Normal patch, the default */
+	GIT_DIFF_FORMAT_EMAIL_NONE = 0,
+
+	/** Don't insert "[PATCH]" in the subject header*/
+	GIT_DIFF_FORMAT_EMAIL_EXCLUDE_SUBJECT_PATCH_MARKER = (1 << 0),
+
+} git_diff_format_email_flags_t;
+
+/**
+ * Options for controlling the formatting of the generated e-mail.
+ */
+typedef struct {
+	unsigned int version;
+
+	/** see `git_diff_format_email_flags_t` above */
+	uint32_t flags;
+
+	/** This patch number */
+	size_t patch_no;
+
+	/** Total number of patches in this series */
+	size_t total_patches;
+
+	/** id to use for the commit */
+	const git_oid *id;
+
+	/** Summary of the change */
+	const char *summary;
+
+	/** Commit message's body */
+	const char *body;
+
+	/** Author of the change */
+	const git_signature *author;
+} git_diff_format_email_options;
+
+#define GIT_DIFF_FORMAT_EMAIL_OPTIONS_VERSION 1
+#define GIT_DIFF_FORMAT_EMAIL_OPTIONS_INIT {GIT_DIFF_FORMAT_EMAIL_OPTIONS_VERSION, 0, 1, 1, NULL, NULL, NULL, NULL}
+
+/**
+ * Create an e-mail ready patch from a diff.
+ *
+ * @deprecated git_email_create_from_diff
+ * @see git_email_create_from_diff
+ */
+GIT_EXTERN(int) git_diff_format_email(
+	git_buf *out,
+	git_diff *diff,
+	const git_diff_format_email_options *opts);
+
+/**
+ * Create an e-mail ready patch for a commit.
+ *
+ * @deprecated git_email_create_from_commit
+ * @see git_email_create_from_commit
+ */
+GIT_EXTERN(int) git_diff_commit_as_email(
+	git_buf *out,
+	git_repository *repo,
+	git_commit *commit,
+	size_t patch_no,
+	size_t total_patches,
+	uint32_t flags,
+	const git_diff_options *diff_opts);
+
+/**
+ * Initialize git_diff_format_email_options structure
+ *
+ * Initializes a `git_diff_format_email_options` with default values. Equivalent
+ * to creating an instance with GIT_DIFF_FORMAT_EMAIL_OPTIONS_INIT.
+ *
+ * @param opts The `git_blame_options` struct to initialize.
+ * @param version The struct version; pass `GIT_DIFF_FORMAT_EMAIL_OPTIONS_VERSION`.
+ * @return Zero on success; -1 on failure.
+ */
+GIT_EXTERN(int) git_diff_format_email_options_init(
+	git_diff_format_email_options *opts,
+	unsigned int version);
+
+/**@}*/
+
 /** @name Deprecated Error Functions and Constants
  *
  * These functions and enumeration values are retained for backward
diff --git a/include/git2/diff.h b/include/git2/diff.h
index 9497793..a0a15e7 100644
--- a/include/git2/diff.h
+++ b/include/git2/diff.h
@@ -1377,99 +1377,6 @@ GIT_EXTERN(int) git_diff_stats_to_buf(
 GIT_EXTERN(void) git_diff_stats_free(git_diff_stats *stats);
 
 /**
- * Formatting options for diff e-mail generation
- */
-typedef enum {
-	/** Normal patch, the default */
-	GIT_DIFF_FORMAT_EMAIL_NONE = 0,
-
-	/** Don't insert "[PATCH]" in the subject header*/
-	GIT_DIFF_FORMAT_EMAIL_EXCLUDE_SUBJECT_PATCH_MARKER = (1 << 0),
-
-} git_diff_format_email_flags_t;
-
-/**
- * Options for controlling the formatting of the generated e-mail.
- */
-typedef struct {
-	unsigned int version;
-
-	/** see `git_diff_format_email_flags_t` above */
-	uint32_t flags;
-
-	/** This patch number */
-	size_t patch_no;
-
-	/** Total number of patches in this series */
-	size_t total_patches;
-
-	/** id to use for the commit */
-	const git_oid *id;
-
-	/** Summary of the change */
-	const char *summary;
-
-	/** Commit message's body */
-	const char *body;
-
-	/** Author of the change */
-	const git_signature *author;
-} git_diff_format_email_options;
-
-#define GIT_DIFF_FORMAT_EMAIL_OPTIONS_VERSION 1
-#define GIT_DIFF_FORMAT_EMAIL_OPTIONS_INIT {GIT_DIFF_FORMAT_EMAIL_OPTIONS_VERSION, 0, 1, 1, NULL, NULL, NULL, NULL}
-
-/**
- * Create an e-mail ready patch from a diff.
- *
- * @param out buffer to store the e-mail patch in
- * @param diff containing the commit
- * @param opts structure with options to influence content and formatting.
- * @return 0 or an error code
- */
-GIT_EXTERN(int) git_diff_format_email(
-	git_buf *out,
-	git_diff *diff,
-	const git_diff_format_email_options *opts);
-
-/**
- * Create an e-mail ready patch for a commit.
- *
- * Does not support creating patches for merge commits (yet).
- *
- * @param out buffer to store the e-mail patch in
- * @param repo containing the commit
- * @param commit pointer to up commit
- * @param patch_no patch number of the commit
- * @param total_patches total number of patches in the patch set
- * @param flags determines the formatting of the e-mail
- * @param diff_opts structure with options to influence diff or NULL for defaults.
- * @return 0 or an error code
- */
-GIT_EXTERN(int) git_diff_commit_as_email(
-	git_buf *out,
-	git_repository *repo,
-	git_commit *commit,
-	size_t patch_no,
-	size_t total_patches,
-	uint32_t flags,
-	const git_diff_options *diff_opts);
-
-/**
- * Initialize git_diff_format_email_options structure
- *
- * Initializes a `git_diff_format_email_options` with default values. Equivalent
- * to creating an instance with GIT_DIFF_FORMAT_EMAIL_OPTIONS_INIT.
- *
- * @param opts The `git_blame_options` struct to initialize.
- * @param version The struct version; pass `GIT_DIFF_FORMAT_EMAIL_OPTIONS_VERSION`.
- * @return Zero on success; -1 on failure.
- */
-GIT_EXTERN(int) git_diff_format_email_options_init(
-	git_diff_format_email_options *opts,
-	unsigned int version);
-
-/**
  * Patch ID options structure
  *
  * Initialize with `GIT_PATCHID_OPTIONS_INIT`. Alternatively, you can
diff --git a/include/git2/email.h b/include/git2/email.h
new file mode 100644
index 0000000..b56be5d
--- /dev/null
+++ b/include/git2/email.h
@@ -0,0 +1,127 @@
+/*
+ * Copyright (C) the libgit2 contributors. All rights reserved.
+ *
+ * This file is part of libgit2, distributed under the GNU GPL v2 with
+ * a Linking Exception. For full terms see the included COPYING file.
+ */
+#ifndef INCLUDE_git_email_h__
+#define INCLUDE_git_email_h__
+
+#include "common.h"
+
+/**
+ * @file git2/email.h
+ * @brief Git email formatting and application routines.
+ * @ingroup Git
+ * @{
+ */
+GIT_BEGIN_DECL
+
+/**
+ * Formatting options for diff e-mail generation
+ */
+typedef enum {
+	/** Normal patch, the default */
+	GIT_EMAIL_CREATE_DEFAULT = 0,
+
+	/** Do not include patch numbers in the subject prefix. */
+	GIT_EMAIL_CREATE_OMIT_NUMBERS = (1u << 0),
+
+	/**
+	 * Include numbers in the subject prefix even when the
+	 * patch is for a single commit (1/1).
+	 */
+	GIT_EMAIL_CREATE_ALWAYS_NUMBER = (1u << 1),
+
+	/** Do not perform rename or similarity detection. */
+	GIT_EMAIL_CREATE_NO_RENAMES = (1u << 2),
+} git_email_create_flags_t;
+
+/**
+ * Options for controlling the formatting of the generated e-mail.
+ */
+typedef struct {
+	unsigned int version;
+
+	/** see `git_email_create_flags_t` above */
+	uint32_t flags;
+
+	/** Options to use when creating diffs */
+	git_diff_options diff_opts;
+
+	/** Options for finding similarities within diffs */
+	git_diff_find_options diff_find_opts;
+
+	/**
+	 * The subject prefix, by default "PATCH".  If set to an empty
+	 * string ("") then only the patch numbers will be shown in the
+	 * prefix.  If the subject_prefix is empty and patch numbers
+	 * are not being shown, the prefix will be omitted entirely.
+	 */
+	const char *subject_prefix;
+
+	/**
+	 * The starting patch number; this cannot be 0.  By default,
+	 * this is 1.
+	 */
+	size_t start_number;
+
+	/** The "re-roll" number.  By default, there is no re-roll. */
+	size_t reroll_number;
+} git_email_create_options;
+
+/*
+ * By default, our options include rename detection and binary
+ * diffs to match `git format-patch`.
+ */
+#define GIT_EMAIL_CREATE_OPTIONS_VERSION 1
+#define GIT_EMAIL_CREATE_OPTIONS_INIT \
+{ \
+	GIT_EMAIL_CREATE_OPTIONS_VERSION, \
+	GIT_EMAIL_CREATE_DEFAULT, \
+	{ GIT_DIFF_OPTIONS_VERSION, GIT_DIFF_SHOW_BINARY, GIT_SUBMODULE_IGNORE_UNSPECIFIED, {NULL,0}, NULL, NULL, NULL, 3 }, \
+	GIT_DIFF_FIND_OPTIONS_INIT \
+}
+
+/**
+ * Create a diff for a commit in mbox format for sending via email.
+ *
+ * @param out buffer to store the e-mail patch in
+ * @param diff the changes to include in the email
+ * @param patch_idx the patch index
+ * @param patch_count the total number of patches that will be included
+ * @param commit_id the commit id for this change
+ * @param summary the commit message for this change
+ * @param body optional text to include above the diffstat
+ * @param author the person who authored this commit
+ * @param opts email creation options
+ */
+GIT_EXTERN(int) git_email_create_from_diff(
+	git_buf *out,
+	git_diff *diff,
+	size_t patch_idx,
+	size_t patch_count,
+	const git_oid *commit_id,
+	const char *summary,
+	const char *body,
+	const git_signature *author,
+	const git_email_create_options *opts);
+
+/**
+ * Create a diff for a commit in mbox format for sending via email.
+ * The commit must not be a merge commit.
+ *
+ * @param out buffer to store the e-mail patch in
+ * @param commit commit to create a patch for
+ * @param opts email creation options
+ */
+GIT_EXTERN(int) git_email_create_from_commit(
+	git_buf *out,
+	git_commit *commit,
+	const git_email_create_options *opts);
+
+GIT_END_DECL
+
+/** @} */
+
+#endif
diff --git a/include/git2/sys/email.h b/include/git2/sys/email.h
new file mode 100644
index 0000000..6f4a286
--- /dev/null
+++ b/include/git2/sys/email.h
@@ -0,0 +1,45 @@
+/*
+ * Copyright (C) the libgit2 contributors. All rights reserved.
+ *
+ * This file is part of libgit2, distributed under the GNU GPL v2 with
+ * a Linking Exception. For full terms see the included COPYING file.
+ */
+#ifndef INCLUDE_sys_git_email_h__
+#define INCLUDE_sys_git_email_h__
+
+/**
+ * @file git2/sys/email.h
+ * @brief Advanced git email creation routines
+ * @defgroup git_email Advanced git email creation routines
+ * @ingroup Git
+ * @{
+ */
+GIT_BEGIN_DECL
+
+/**
+ * Create a diff for a commit in mbox format for sending via email.
+ *
+ * @param out buffer to store the e-mail patch in
+ * @param diff the changes to include in the email
+ * @param patch_idx the patch index
+ * @param patch_count the total number of patches that will be included
+ * @param commit_id the commit id for this change
+ * @param summary the commit message for this change
+ * @param body optional text to include above the diffstat
+ * @param author the person who authored this commit
+ * @param opts email creation options
+ */
+GIT_EXTERN(int) git_email_create_from_diff(
+	git_buf *out,
+	git_diff *diff,
+	size_t patch_idx,
+	size_t patch_count,
+	const git_oid *commit_id,
+	const char *summary,
+	const char *body,
+	const git_signature *author,
+	const git_email_create_options *opts);
+
+/** @} */
+GIT_END_DECL
+#endif
diff --git a/src/buffer.c b/src/buffer.c
index ab2a613..a57df12 100644
--- a/src/buffer.c
+++ b/src/buffer.c
@@ -600,6 +600,13 @@ void git_buf_shorten(git_buf *buf, size_t amount)
 		git_buf_clear(buf);
 }
 
+void git_buf_truncate_at_char(git_buf *buf, char separator)
+{
+	ssize_t idx = git_buf_find(buf, separator);
+	if (idx >= 0)
+		git_buf_truncate(buf, (size_t)idx);
+}
+
 void git_buf_rtruncate_at_char(git_buf *buf, char separator)
 {
 	ssize_t idx = git_buf_rfind_next(buf, separator);
diff --git a/src/buffer.h b/src/buffer.h
index 7faa9fd..a356beb 100644
--- a/src/buffer.h
+++ b/src/buffer.h
@@ -171,6 +171,7 @@ void git_buf_consume_bytes(git_buf *buf, size_t len);
 void git_buf_consume(git_buf *buf, const char *end);
 void git_buf_truncate(git_buf *buf, size_t len);
 void git_buf_shorten(git_buf *buf, size_t amount);
+void git_buf_truncate_at_char(git_buf *buf, char separator);
 void git_buf_rtruncate_at_char(git_buf *path, char separator);
 
 /** General join with separator */
diff --git a/src/diff.c b/src/diff.c
index 4085c5f..30b9f64 100644
--- a/src/diff.c
+++ b/src/diff.c
@@ -7,11 +7,15 @@
 
 #include "diff.h"
 
-#include "git2/version.h"
-#include "diff_generate.h"
+#include "common.h"
 #include "patch.h"
+#include "email.h"
 #include "commit.h"
 #include "index.h"
+#include "diff_generate.h"
+
+#include "git2/version.h"
+#include "git2/email.h"
 
 struct patch_id_args {
 	git_hash_ctx ctx;
@@ -150,97 +154,14 @@ int git_diff_foreach(
 	return error;
 }
 
-static int diff_format_email_append_header_tobuf(
-	git_buf *out,
-	const git_oid *id,
-	const git_signature *author,
-	const char *summary,
-	const char *body,
-	size_t patch_no,
-	size_t total_patches,
-	bool exclude_patchno_marker)
-{
-	char idstr[GIT_OID_HEXSZ + 1];
-	char date_str[GIT_DATE_RFC2822_SZ];
-	int error = 0;
-
-	git_oid_fmt(idstr, id);
-	idstr[GIT_OID_HEXSZ] = '\0';
-
-	if ((error = git__date_rfc2822_fmt(date_str, sizeof(date_str),
-		&author->when)) < 0)
-		return error;
-
-	error = git_buf_printf(out,
-				"From %s Mon Sep 17 00:00:00 2001\n" \
-				"From: %s <%s>\n" \
-				"Date: %s\n" \
-				"Subject: ",
-				idstr,
-				author->name, author->email,
-				date_str);
-
-	if (error < 0)
-		return error;
-
-	if (!exclude_patchno_marker) {
-		if (total_patches == 1) {
-			error = git_buf_puts(out, "[PATCH] ");
-		} else {
-			error = git_buf_printf(out, "[PATCH %"PRIuZ"/%"PRIuZ"] ",
-				patch_no, total_patches);
-		}
-
-		if (error < 0)
-			return error;
-	}
-
-	error = git_buf_printf(out, "%s\n\n", summary);
-
-	if (body) {
-		git_buf_puts(out, body);
-
-		if (out->ptr[out->size - 1] != '\n')
-			git_buf_putc(out, '\n');
-	}
-
-	return error;
-}
-
-static int diff_format_email_append_patches_tobuf(
-	git_buf *out,
-	git_diff *diff)
-{
-	size_t i, deltas;
-	int error = 0;
-
-	deltas = git_diff_num_deltas(diff);
-
-	for (i = 0; i < deltas; ++i) {
-		git_patch *patch = NULL;
-
-		if ((error = git_patch_from_diff(&patch, diff, i)) >= 0)
-			error = git_patch_to_buf(out, patch);
-
-		git_patch_free(patch);
-
-		if (error < 0)
-			break;
-	}
-
-	return error;
-}
+#ifndef GIT_DEPRECATE_HARD
 
 int git_diff_format_email(
 	git_buf *out,
 	git_diff *diff,
 	const git_diff_format_email_options *opts)
 {
-	git_diff_stats *stats = NULL;
-	char *summary = NULL, *loc = NULL;
-	bool ignore_marker;
-	unsigned int format_flags = 0;
-	size_t allocsize;
+	git_email_create_options email_create_opts = GIT_EMAIL_CREATE_OPTIONS_INIT;
 	int error;
 
 	GIT_ASSERT_ARG(out);
@@ -251,64 +172,13 @@ int git_diff_format_email(
 		GIT_DIFF_FORMAT_EMAIL_OPTIONS_VERSION,
 		"git_format_email_options");
 
-	ignore_marker = (opts->flags &
-		GIT_DIFF_FORMAT_EMAIL_EXCLUDE_SUBJECT_PATCH_MARKER) != 0;
-
-	if (!ignore_marker) {
-		if (opts->patch_no > opts->total_patches) {
-			git_error_set(GIT_ERROR_INVALID,
-				"patch %"PRIuZ" out of range. max %"PRIuZ,
-				opts->patch_no, opts->total_patches);
-			return -1;
-		}
+	if ((opts->flags & GIT_DIFF_FORMAT_EMAIL_EXCLUDE_SUBJECT_PATCH_MARKER) != 0)
+		email_create_opts.subject_prefix = "";
 
-		if (opts->patch_no == 0) {
-			git_error_set(GIT_ERROR_INVALID,
-				"invalid patch no %"PRIuZ". should be >0", opts->patch_no);
-			return -1;
-		}
-	}
 
-	/* the summary we receive may not be clean.
-	 * it could potentially contain new line characters
-	 * or not be set, sanitize, */
-	if ((loc = strpbrk(opts->summary, "\r\n")) != NULL) {
-		size_t offset = 0;
-
-		if ((offset = (loc - opts->summary)) == 0) {
-			git_error_set(GIT_ERROR_INVALID, "summary is empty");
-			error = -1;
-			goto on_error;
-		}
-
-		GIT_ERROR_CHECK_ALLOC_ADD(&allocsize, offset, 1);
-		summary = git__calloc(allocsize, sizeof(char));
-		GIT_ERROR_CHECK_ALLOC(summary);
-
-		strncpy(summary, opts->summary, offset);
-	}
-
-	error = diff_format_email_append_header_tobuf(out,
-		opts->id, opts->author, summary == NULL ? opts->summary : summary,
-		opts->body, opts->patch_no, opts->total_patches, ignore_marker);
-
-	if (error < 0)
-		goto on_error;
-
-	format_flags = GIT_DIFF_STATS_FULL | GIT_DIFF_STATS_INCLUDE_SUMMARY;
-
-	if ((error = git_buf_puts(out, "---\n")) < 0 ||
-		(error = git_diff_get_stats(&stats, diff)) < 0 ||
-		(error = git_diff_stats_to_buf(out, stats, format_flags, 0)) < 0 ||
-		(error = git_buf_putc(out, '\n')) < 0 ||
-		(error = diff_format_email_append_patches_tobuf(out, diff)) < 0)
-			goto on_error;
-
-	error = git_buf_puts(out, "--\nlibgit2 " LIBGIT2_VERSION "\n\n");
-
-on_error:
-	git__free(summary);
-	git_diff_stats_free(stats);
+	error = git_email__append_from_diff(out, diff, opts->patch_no,
+		opts->total_patches, opts->id, opts->summary, opts->body,
+		opts->author, &email_create_opts);
 
 	return error;
 }
@@ -323,60 +193,43 @@ int git_diff_commit_as_email(
 	const git_diff_options *diff_opts)
 {
 	git_diff *diff = NULL;
-	git_diff_format_email_options opts =
-		GIT_DIFF_FORMAT_EMAIL_OPTIONS_INIT;
+	git_email_create_options opts = GIT_EMAIL_CREATE_OPTIONS_INIT;
+	const git_oid *commit_id;
+	const char *summary, *body;
+	const git_signature *author;
 	int error;
 
 	GIT_ASSERT_ARG(out);
 	GIT_ASSERT_ARG(repo);
 	GIT_ASSERT_ARG(commit);
 
-	opts.flags = flags;
-	opts.patch_no = patch_no;
-	opts.total_patches = total_patches;
-	opts.id = git_commit_id(commit);
-	opts.summary = git_commit_summary(commit);
-	opts.body = git_commit_body(commit);
-	opts.author = git_commit_author(commit);
+	commit_id = git_commit_id(commit);
+	summary = git_commit_summary(commit);
+	body = git_commit_body(commit);
+	author = git_commit_author(commit);
+
+	if ((flags & GIT_DIFF_FORMAT_EMAIL_EXCLUDE_SUBJECT_PATCH_MARKER) != 0)
+		opts.subject_prefix = "";
 
 	if ((error = git_diff__commit(&diff, repo, commit, diff_opts)) < 0)
 		return error;
 
-	error = git_diff_format_email(out, diff, &opts);
+	error = git_email_create_from_diff(out, diff, patch_no, total_patches, commit_id, summary, body, author, &opts);
 
 	git_diff_free(diff);
 	return error;
 }
 
-int git_diff_options_init(git_diff_options *opts, unsigned int version)
-{
-	GIT_INIT_STRUCTURE_FROM_TEMPLATE(
-		opts, version, git_diff_options, GIT_DIFF_OPTIONS_INIT);
-	return 0;
-}
-
-#ifndef GIT_DEPRECATE_HARD
 int git_diff_init_options(git_diff_options *opts, unsigned int version)
 {
 	return git_diff_options_init(opts, version);
 }
-#endif
 
-int git_diff_find_options_init(
-	git_diff_find_options *opts, unsigned int version)
-{
-	GIT_INIT_STRUCTURE_FROM_TEMPLATE(
-		opts, version, git_diff_find_options, GIT_DIFF_FIND_OPTIONS_INIT);
-	return 0;
-}
-
-#ifndef GIT_DEPRECATE_HARD
 int git_diff_find_init_options(
 	git_diff_find_options *opts, unsigned int version)
 {
 	return git_diff_find_options_init(opts, version);
 }
-#endif
 
 int git_diff_format_email_options_init(
 	git_diff_format_email_options *opts, unsigned int version)
@@ -387,14 +240,29 @@ int git_diff_format_email_options_init(
 	return 0;
 }
 
-#ifndef GIT_DEPRECATE_HARD
 int git_diff_format_email_init_options(
 	git_diff_format_email_options *opts, unsigned int version)
 {
 	return git_diff_format_email_options_init(opts, version);
 }
+
 #endif
 
+int git_diff_options_init(git_diff_options *opts, unsigned int version)
+{
+	GIT_INIT_STRUCTURE_FROM_TEMPLATE(
+		opts, version, git_diff_options, GIT_DIFF_OPTIONS_INIT);
+	return 0;
+}
+
+int git_diff_find_options_init(
+	git_diff_find_options *opts, unsigned int version)
+{
+	GIT_INIT_STRUCTURE_FROM_TEMPLATE(
+		opts, version, git_diff_find_options, GIT_DIFF_FIND_OPTIONS_INIT);
+	return 0;
+}
+
 static int flush_hunk(git_oid *result, git_hash_ctx *ctx)
 {
 	git_oid hash;
diff --git a/src/email.c b/src/email.c
new file mode 100644
index 0000000..8957d9a
--- /dev/null
+++ b/src/email.c
@@ -0,0 +1,300 @@
+/*
+ * Copyright (C) the libgit2 contributors. All rights reserved.
+ *
+ * This file is part of libgit2, distributed under the GNU GPL v2 with
+ * a Linking Exception. For full terms see the included COPYING file.
+ */
+
+#include "email.h"
+
+#include "buffer.h"
+#include "common.h"
+#include "diff_generate.h"
+
+#include "git2/email.h"
+#include "git2/patch.h"
+#include "git2/version.h"
+
+/*
+ * Git uses a "magic" timestamp to indicate that an email message
+ * is from `git format-patch` (or our equivalent).
+ */
+#define EMAIL_TIMESTAMP "Mon Sep 17 00:00:00 2001"
+
+GIT_INLINE(int) include_prefix(
+	size_t patch_count,
+	git_email_create_options *opts)
+{
+	return ((!opts->subject_prefix || *opts->subject_prefix) ||
+	        (opts->flags & GIT_EMAIL_CREATE_ALWAYS_NUMBER) != 0 ||
+	        opts->reroll_number ||
+		(patch_count > 1 && !(opts->flags & GIT_EMAIL_CREATE_OMIT_NUMBERS)));
+}
+
+static int append_prefix(
+	git_buf *out,
+	size_t patch_idx,
+	size_t patch_count,
+	git_email_create_options *opts)
+{
+	const char *subject_prefix = opts->subject_prefix ?
+		opts->subject_prefix : "PATCH";
+
+	git_buf_putc(out, '[');
+
+	if (*subject_prefix)
+		git_buf_puts(out, subject_prefix);
+
+	if (opts->reroll_number) {
+		if (*subject_prefix)
+			git_buf_putc(out, ' ');
+
+		git_buf_printf(out, "v%" PRIuZ, opts->reroll_number);
+	}
+
+	if ((opts->flags & GIT_EMAIL_CREATE_ALWAYS_NUMBER) != 0 ||
+	    (patch_count > 1 && !(opts->flags & GIT_EMAIL_CREATE_OMIT_NUMBERS))) {
+		size_t start_number = opts->start_number ?
+			opts->start_number : 1;
+
+		if (*subject_prefix || opts->reroll_number)
+			git_buf_putc(out, ' ');
+
+		git_buf_printf(out, "%" PRIuZ "/%" PRIuZ,
+		               patch_idx + (start_number - 1),
+		               patch_count + (start_number - 1));
+	}
+
+	git_buf_puts(out, "]");
+
+	return git_buf_oom(out) ? -1 : 0;
+}
+
+static int append_subject(
+	git_buf *out,
+	size_t patch_idx,
+	size_t patch_count,
+	const char *summary,
+	git_email_create_options *opts)
+{
+	bool prefix = include_prefix(patch_count, opts);
+	size_t summary_len = summary ? strlen(summary) : 0;
+	int error;
+
+	if (summary_len) {
+		const char *nl = strchr(summary, '\n');
+
+		if (nl)
+			summary_len = (nl - summary);
+	}
+
+	if ((error = git_buf_puts(out, "Subject: ")) < 0)
+		return error;
+
+	if (prefix &&
+	    (error = append_prefix(out, patch_idx, patch_count, opts)) < 0)
+		return error;
+
+	if (prefix && summary_len && (error = git_buf_putc(out, ' ')) < 0)
+		return error;
+
+	if (summary_len &&
+	    (error = git_buf_put(out, summary, summary_len)) < 0)
+		return error;
+
+	return git_buf_putc(out, '\n');
+}
+
+static int append_header(
+	git_buf *out,
+	size_t patch_idx,
+	size_t patch_count,
+	const git_oid *commit_id,
+	const char *summary,
+	const git_signature *author,
+	git_email_create_options *opts)
+{
+	char id[GIT_OID_HEXSZ];
+	char date[GIT_DATE_RFC2822_SZ];
+	int error;
+
+	if ((error = git_oid_fmt(id, commit_id)) < 0 ||
+	    (error = git_buf_printf(out, "From %.*s %s\n", GIT_OID_HEXSZ, id, EMAIL_TIMESTAMP)) < 0 ||
+	    (error = git_buf_printf(out, "From: %s <%s>\n", author->name, author->email)) < 0 ||
+	    (error = git__date_rfc2822_fmt(date, sizeof(date), &author->when)) < 0 ||
+	    (error = git_buf_printf(out, "Date: %s\n", date)) < 0 ||
+	    (error = append_subject(out, patch_idx, patch_count, summary, opts)) < 0)
+		return error;
+
+	if ((error = git_buf_putc(out, '\n')) < 0)
+		return error;
+
+	return 0;
+}
+
+static int append_body(git_buf *out, const char *body)
+{
+	size_t body_len;
+	int error;
+
+	if (!body)
+		return 0;
+
+	body_len = strlen(body);
+
+	if ((error = git_buf_puts(out, body)) < 0)
+		return error;
+
+	if (body_len && body[body_len - 1] != '\n')
+		error = git_buf_putc(out, '\n');
+
+	return error;
+}
+
+static int append_diffstat(git_buf *out, git_diff *diff)
+{
+	git_diff_stats *stats = NULL;
+	unsigned int format_flags;
+	int error;
+
+	format_flags = GIT_DIFF_STATS_FULL | GIT_DIFF_STATS_INCLUDE_SUMMARY;
+
+	if ((error = git_diff_get_stats(&stats, diff)) == 0 &&
+	    (error = git_diff_stats_to_buf(out, stats, format_flags, 0)) == 0)
+		error = git_buf_putc(out, '\n');
+
+	git_diff_stats_free(stats);
+	return error;
+}
+
+static int append_patches(git_buf *out, git_diff *diff)
+{
+	size_t i, deltas;
+	int error = 0;
+
+	deltas = git_diff_num_deltas(diff);
+
+	for (i = 0; i < deltas; ++i) {
+		git_patch *patch = NULL;
+
+		if ((error = git_patch_from_diff(&patch, diff, i)) >= 0)
+			error = git_patch_to_buf(out, patch);
+
+		git_patch_free(patch);
+
+		if (error < 0)
+			break;
+	}
+
+	return error;
+}
+
+int git_email__append_from_diff(
+	git_buf *out,
+	git_diff *diff,
+	size_t patch_idx,
+	size_t patch_count,
+	const git_oid *commit_id,
+	const char *summary,
+	const char *body,
+	const git_signature *author,
+	const git_email_create_options *given_opts)
+{
+	git_email_create_options opts = GIT_EMAIL_CREATE_OPTIONS_INIT;
+	int error;
+
+	GIT_ASSERT_ARG(out);
+	GIT_ASSERT_ARG(diff);
+	GIT_ASSERT_ARG(!patch_idx || patch_idx <= patch_count);
+	GIT_ASSERT_ARG(commit_id);
+	GIT_ASSERT_ARG(author);
+
+	GIT_ERROR_CHECK_VERSION(given_opts,
+		GIT_EMAIL_CREATE_OPTIONS_VERSION,
+		"git_email_create_options");
+
+	if (given_opts)
+		memcpy(&opts, given_opts, sizeof(git_email_create_options));
+
+	git_buf_sanitize(out);
+	git_buf_clear(out);
+
+	if ((error = append_header(out, patch_idx, patch_count, commit_id, summary, author, &opts)) == 0 &&
+	    (error = append_body(out, body)) == 0 &&
+	    (error = git_buf_puts(out, "---\n")) == 0 &&
+	    (error = append_diffstat(out, diff)) == 0 &&
+	    (error = append_patches(out, diff)) == 0)
+		error = git_buf_puts(out, "--\nlibgit2 " LIBGIT2_VERSION "\n\n");
+
+	return error;
+}
+
+int git_email_create_from_diff(
+	git_buf *out,
+	git_diff *diff,
+	size_t patch_idx,
+	size_t patch_count,
+	const git_oid *commit_id,
+	const char *summary,
+	const char *body,
+	const git_signature *author,
+	const git_email_create_options *given_opts)
+{
+	int error;
+
+	git_buf_sanitize(out);
+	git_buf_clear(out);
+
+	error = git_email__append_from_diff(out, diff, patch_idx,
+		patch_count, commit_id, summary, body, author,
+		given_opts);
+
+	return error;
+}
+
+int git_email_create_from_commit(
+	git_buf *out,
+	git_commit *commit,
+	const git_email_create_options *given_opts)
+{
+	git_email_create_options opts = GIT_EMAIL_CREATE_OPTIONS_INIT;
+	git_diff *diff = NULL;
+	git_repository *repo;
+	git_diff_options *diff_opts;
+	git_diff_find_options *find_opts;
+	const git_signature *author;
+	const char *summary, *body;
+	const git_oid *commit_id;
+	int error = -1;
+
+	GIT_ASSERT_ARG(out);
+	GIT_ASSERT_ARG(commit);
+
+	GIT_ERROR_CHECK_VERSION(given_opts,
+		GIT_EMAIL_CREATE_OPTIONS_VERSION,
+		"git_email_create_options");
+
+	if (given_opts)
+		memcpy(&opts, given_opts, sizeof(git_email_create_options));
+
+	repo = git_commit_owner(commit);
+	author = git_commit_author(commit);
+	summary = git_commit_summary(commit);
+	body = git_commit_body(commit);
+	commit_id = git_commit_id(commit);
+	diff_opts = &opts.diff_opts;
+	find_opts = &opts.diff_find_opts;
+
+	if ((error = git_diff__commit(&diff, repo, commit, diff_opts)) < 0)
+		goto done;
+
+	if ((opts.flags & GIT_EMAIL_CREATE_NO_RENAMES) == 0 &&
+	    (error = git_diff_find_similar(diff, find_opts)) < 0)
+		goto done;
+
+	error = git_email_create_from_diff(out, diff, 1, 1, commit_id, summary, body, author, &opts);
+
+done:
+	git_diff_free(diff);
+	return error;
+}
diff --git a/src/email.h b/src/email.h
new file mode 100644
index 0000000..7aeb462
--- /dev/null
+++ b/src/email.h
@@ -0,0 +1,25 @@
+/*
+ * Copyright (C) the libgit2 contributors. All rights reserved.
+ *
+ * This file is part of libgit2, distributed under the GNU GPL v2 with
+ * a Linking Exception. For full terms see the included COPYING file.
+ */
+#ifndef INCLUDE_email_h__
+#define INCLUDE_email_h__
+
+#include "common.h"
+
+#include "git2/email.h"
+
+extern int git_email__append_from_diff(
+	git_buf *out,
+	git_diff *diff,
+	size_t patch_idx,
+	size_t patch_count,
+	const git_oid *commit_id,
+	const char *summary,
+	const char *body,
+	const git_signature *author,
+	const git_email_create_options *given_opts);
+
+#endif
diff --git a/tests/diff/format_email.c b/tests/diff/format_email.c
index bdfc4ca..ea7aa07 100644
--- a/tests/diff/format_email.c
+++ b/tests/diff/format_email.c
@@ -18,6 +18,7 @@ void test_diff_format_email__cleanup(void)
 	cl_git_sandbox_cleanup();
 }
 
+#ifndef GIT_DEPRECATE_HARD
 static void assert_email_match(
 	const char *expected,
 	const char *oidstr,
@@ -51,9 +52,11 @@ static void assert_email_match(
 	git_commit_free(commit);
 	git_buf_dispose(&buf);
 }
+#endif
 
 void test_diff_format_email__simple(void)
 {
+#ifndef GIT_DEPRECATE_HARD
 	git_diff_format_email_options opts = GIT_DIFF_FORMAT_EMAIL_OPTIONS_INIT;
 	const char *email =
 	"From 9264b96c6d104d0e07ae33d3007b6a48246c6f92 Mon Sep 17 00:00:00 2001\n" \
@@ -96,10 +99,12 @@ void test_diff_format_email__simple(void)
 
 	assert_email_match(
 		email, "9264b96c6d104d0e07ae33d3007b6a48246c6f92", &opts);
+#endif
 }
 
 void test_diff_format_email__with_message(void)
 {
+#ifndef GIT_DEPRECATE_HARD
 	git_diff_format_email_options opts = GIT_DIFF_FORMAT_EMAIL_OPTIONS_INIT;
 	const char *email = "From 627e7e12d87e07a83fad5b6bfa25e86ead4a5270 Mon Sep 17 00:00:00 2001\n" \
 	"From: Patrick Steinhardt <ps@pks.im>\n" \
@@ -136,11 +141,13 @@ void test_diff_format_email__with_message(void)
 
 	assert_email_match(
 		email, "627e7e12d87e07a83fad5b6bfa25e86ead4a5270", &opts);
+#endif
 }
 
 
 void test_diff_format_email__multiple(void)
 {
+#ifndef GIT_DEPRECATE_HARD
 	git_oid oid;
 	git_commit *commit = NULL;
 	git_diff *diff = NULL;
@@ -256,10 +263,12 @@ void test_diff_format_email__multiple(void)
 	git_diff_free(diff);
 	git_commit_free(commit);
 	git_buf_dispose(&buf);
+#endif
 }
 
 void test_diff_format_email__exclude_marker(void)
 {
+#ifndef GIT_DEPRECATE_HARD
 	git_diff_format_email_options opts = GIT_DIFF_FORMAT_EMAIL_OPTIONS_INIT;
 	const char *email =
 	"From 9264b96c6d104d0e07ae33d3007b6a48246c6f92 Mon Sep 17 00:00:00 2001\n" \
@@ -304,10 +313,12 @@ void test_diff_format_email__exclude_marker(void)
 
 	assert_email_match(
 		email, "9264b96c6d104d0e07ae33d3007b6a48246c6f92", &opts);
+#endif
 }
 
 void test_diff_format_email__invalid_no(void)
 {
+#ifndef GIT_DEPRECATE_HARD
 	git_oid oid;
 	git_commit *commit = NULL;
 	git_diff *diff = NULL;
@@ -327,15 +338,16 @@ void test_diff_format_email__invalid_no(void)
 	cl_git_pass(git_diff__commit(&diff, repo, commit, NULL));
 	cl_git_fail(git_diff_format_email(&buf, diff, &opts));
 	cl_git_fail(git_diff_commit_as_email(&buf, repo, commit, 2, 1, 0, NULL));
-	cl_git_fail(git_diff_commit_as_email(&buf, repo, commit, 0, 0, 0, NULL));
 
 	git_diff_free(diff);
 	git_commit_free(commit);
 	git_buf_dispose(&buf);
+#endif
 }
 
 void test_diff_format_email__mode_change(void)
 {
+#ifndef GIT_DEPRECATE_HARD
 	git_diff_format_email_options opts = GIT_DIFF_FORMAT_EMAIL_OPTIONS_INIT;
 	const char *email =
 	"From 7ade76dd34bba4733cf9878079f9fd4a456a9189 Mon Sep 17 00:00:00 2001\n" \
@@ -357,10 +369,12 @@ void test_diff_format_email__mode_change(void)
 
 	assert_email_match(
 		email, "7ade76dd34bba4733cf9878079f9fd4a456a9189", &opts);
+#endif
 }
 
 void test_diff_format_email__rename_add_remove(void)
 {
+#ifndef GIT_DEPRECATE_HARD
 	git_diff_format_email_options opts = GIT_DIFF_FORMAT_EMAIL_OPTIONS_INIT;
 	const char *email =
 	"From 6e05acc5a5dab507d91a0a0cc0fb05a3dd98892d Mon Sep 17 00:00:00 2001\n" \
@@ -427,10 +441,12 @@ void test_diff_format_email__rename_add_remove(void)
 
 	assert_email_match(
 		email, "6e05acc5a5dab507d91a0a0cc0fb05a3dd98892d", &opts);
+#endif
 }
 
 void test_diff_format_email__multiline_summary(void)
 {
+#ifndef GIT_DEPRECATE_HARD
 	git_diff_format_email_options opts = GIT_DIFF_FORMAT_EMAIL_OPTIONS_INIT;
 	const char *email =
 	"From 9264b96c6d104d0e07ae33d3007b6a48246c6f92 Mon Sep 17 00:00:00 2001\n" \
@@ -475,10 +491,12 @@ void test_diff_format_email__multiline_summary(void)
 
 	assert_email_match(
 		email, "9264b96c6d104d0e07ae33d3007b6a48246c6f92", &opts);
+#endif
 }
 
 void test_diff_format_email__binary(void)
 {
+#ifndef GIT_DEPRECATE_HARD
 	git_diff_format_email_options opts = GIT_DIFF_FORMAT_EMAIL_OPTIONS_INIT;
 	const char *email =
 	"From 8d7523f6fcb2404257889abe0d96f093d9f524f9 Mon Sep 17 00:00:00 2001\n" \
@@ -501,5 +519,6 @@ void test_diff_format_email__binary(void)
 
 	assert_email_match(
 		email, "8d7523f6fcb2404257889abe0d96f093d9f524f9", &opts);
+#endif
 }
 
diff --git a/tests/email/create.c b/tests/email/create.c
new file mode 100644
index 0000000..ccf79c2
--- /dev/null
+++ b/tests/email/create.c
@@ -0,0 +1,363 @@
+#include "clar.h"
+#include "clar_libgit2.h"
+
+#include "buffer.h"
+#include "diff_generate.h"
+
+static git_repository *repo;
+
+void test_email_create__initialize(void)
+{
+	repo = cl_git_sandbox_init("diff_format_email");
+}
+
+void test_email_create__cleanup(void)
+{
+	cl_git_sandbox_cleanup();
+}
+
+static void email_for_commit(
+	git_buf *out,
+	const char *commit_id,
+	git_email_create_options *opts)
+{
+	git_oid oid;
+	git_commit *commit = NULL;
+	git_diff *diff = NULL;
+
+	git_oid_fromstr(&oid, commit_id);
+
+	cl_git_pass(git_commit_lookup(&commit, repo, &oid));
+
+	cl_git_pass(git_email_create_from_commit(out, commit, opts));
+
+	git_diff_free(diff);
+	git_commit_free(commit);
+}
+
+static void assert_email_match(
+	const char *expected,
+	const char *commit_id,
+	git_email_create_options *opts)
+{
+	git_buf buf = GIT_BUF_INIT;
+
+	email_for_commit(&buf, commit_id, opts);
+	cl_assert_equal_s(expected, git_buf_cstr(&buf));
+
+	git_buf_dispose(&buf);
+}
+
+static void assert_subject_match(
+	const char *expected,
+	const char *commit_id,
+	git_email_create_options *opts)
+{
+	git_buf buf = GIT_BUF_INIT;
+	const char *loc;
+
+	email_for_commit(&buf, commit_id, opts);
+
+	cl_assert((loc = strstr(buf.ptr, "\nSubject: ")) != NULL);
+	git_buf_consume(&buf, (loc + 10));
+	git_buf_truncate_at_char(&buf, '\n');
+
+	cl_assert_equal_s(expected, git_buf_cstr(&buf));
+
+	git_buf_dispose(&buf);
+}
+
+void test_email_create__commit(void)
+{
+	const char *expected =
+	"From 9264b96c6d104d0e07ae33d3007b6a48246c6f92 Mon Sep 17 00:00:00 2001\n" \
+	"From: Jacques Germishuys <jacquesg@striata.com>\n" \
+	"Date: Wed, 9 Apr 2014 20:57:01 +0200\n" \
+	"Subject: [PATCH] Modify some content\n" \
+	"\n" \
+	"---\n" \
+	" file1.txt | 8 +++++---\n" \
+	" 1 file changed, 5 insertions(+), 3 deletions(-)\n" \
+	"\n" \
+	"diff --git a/file1.txt b/file1.txt\n" \
+	"index 94aaae8..af8f41d 100644\n" \
+	"--- a/file1.txt\n" \
+	"+++ b/file1.txt\n" \
+	"@@ -1,15 +1,17 @@\n" \
+	" file1.txt\n" \
+	" file1.txt\n" \
+	"+_file1.txt_\n" \
+	" file1.txt\n" \
+	" file1.txt\n" \
+	" file1.txt\n" \
+	" file1.txt\n" \
+	"+\n" \
+	"+\n" \
+	" file1.txt\n" \
+	" file1.txt\n" \
+	" file1.txt\n" \
+	" file1.txt\n" \
+	" file1.txt\n" \
+	"-file1.txt\n" \
+	"-file1.txt\n" \
+	"-file1.txt\n" \
+	"+_file1.txt_\n" \
+	"+_file1.txt_\n" \
+	" file1.txt\n" \
+	"--\n" \
+	"libgit2 " LIBGIT2_VERSION "\n" \
+	"\n";
+
+	assert_email_match(
+		expected, "9264b96c6d104d0e07ae33d3007b6a48246c6f92", NULL);
+}
+
+void test_email_create__rename(void)
+{
+	const char *expected =
+	"From 6e05acc5a5dab507d91a0a0cc0fb05a3dd98892d Mon Sep 17 00:00:00 2001\n" \
+	"From: Jacques Germishuys <jacquesg@striata.com>\n" \
+	"Date: Wed, 9 Apr 2014 21:15:56 +0200\n" \
+	"Subject: [PATCH] Renamed file1.txt -> file1.txt.renamed\n" \
+	"\n" \
+	"---\n" \
+	" file1.txt => file1.txt.renamed | 4 ++--\n" \
+	" 1 file changed, 2 insertions(+), 2 deletions(-)\n" \
+	"\n" \
+	"diff --git a/file1.txt b/file1.txt.renamed\n" \
+	"similarity index 86%\n" \
+	"rename from file1.txt\n" \
+	"rename to file1.txt.renamed\n" \
+	"index af8f41d..a97157a 100644\n" \
+	"--- a/file1.txt\n" \
+	"+++ b/file1.txt.renamed\n" \
+	"@@ -3,13 +3,13 @@ file1.txt\n" \
+	" _file1.txt_\n" \
+	" file1.txt\n" \
+	" file1.txt\n" \
+	"-file1.txt\n" \
+	"+file1.txt_renamed\n" \
+	" file1.txt\n" \
+	" \n" \
+	" \n" \
+	" file1.txt\n" \
+	" file1.txt\n" \
+	"-file1.txt\n" \
+	"+file1.txt_renamed\n" \
+	" file1.txt\n" \
+	" file1.txt\n" \
+	" _file1.txt_\n" \
+	"--\n" \
+	"libgit2 " LIBGIT2_VERSION "\n" \
+	"\n";
+
+	assert_email_match(expected, "6e05acc5a5dab507d91a0a0cc0fb05a3dd98892d", NULL);
+}
+
+void test_email_create__rename_as_add_delete(void)
+{
+	const char *expected =
+	"From 6e05acc5a5dab507d91a0a0cc0fb05a3dd98892d Mon Sep 17 00:00:00 2001\n" \
+	"From: Jacques Germishuys <jacquesg@striata.com>\n" \
+	"Date: Wed, 9 Apr 2014 21:15:56 +0200\n" \
+	"Subject: [PATCH] Renamed file1.txt -> file1.txt.renamed\n" \
+	"\n" \
+	"---\n" \
+	" file1.txt         | 17 -----------------\n" \
+	" file1.txt.renamed | 17 +++++++++++++++++\n" \
+	" 2 files changed, 17 insertions(+), 17 deletions(-)\n" \
+	" delete mode 100644 file1.txt\n" \
+	" create mode 100644 file1.txt.renamed\n" \
+	"\n" \
+	"diff --git a/file1.txt b/file1.txt\n" \
+	"deleted file mode 100644\n" \
+	"index af8f41d..0000000\n" \
+	"--- a/file1.txt\n" \
+	"+++ /dev/null\n" \
+	"@@ -1,17 +0,0 @@\n" \
+	"-file1.txt\n" \
+	"-file1.txt\n" \
+	"-_file1.txt_\n" \
+	"-file1.txt\n" \
+	"-file1.txt\n" \
+	"-file1.txt\n" \
+	"-file1.txt\n" \
+	"-\n" \
+	"-\n" \
+	"-file1.txt\n" \
+	"-file1.txt\n" \
+	"-file1.txt\n" \
+	"-file1.txt\n" \
+	"-file1.txt\n" \
+	"-_file1.txt_\n" \
+	"-_file1.txt_\n" \
+	"-file1.txt\n" \
+	"diff --git a/file1.txt.renamed b/file1.txt.renamed\n" \
+	"new file mode 100644\n" \
+	"index 0000000..a97157a\n" \
+	"--- /dev/null\n" \
+	"+++ b/file1.txt.renamed\n" \
+	"@@ -0,0 +1,17 @@\n" \
+	"+file1.txt\n" \
+	"+file1.txt\n" \
+	"+_file1.txt_\n" \
+	"+file1.txt\n" \
+	"+file1.txt\n" \
+	"+file1.txt_renamed\n" \
+	"+file1.txt\n" \
+	"+\n" \
+	"+\n" \
+	"+file1.txt\n" \
+	"+file1.txt\n" \
+	"+file1.txt_renamed\n" \
+	"+file1.txt\n" \
+	"+file1.txt\n" \
+	"+_file1.txt_\n" \
+	"+_file1.txt_\n" \
+	"+file1.txt\n" \
+	"--\n" \
+	"libgit2 " LIBGIT2_VERSION "\n" \
+	"\n";
+
+	git_email_create_options opts = GIT_EMAIL_CREATE_OPTIONS_INIT;
+	opts.flags |= GIT_EMAIL_CREATE_NO_RENAMES;
+
+	assert_email_match(expected, "6e05acc5a5dab507d91a0a0cc0fb05a3dd98892d", &opts);
+}
+
+void test_email_create__binary(void)
+{
+	const char *expected =
+	"From 8d7523f6fcb2404257889abe0d96f093d9f524f9 Mon Sep 17 00:00:00 2001\n" \
+	"From: Jacques Germishuys <jacquesg@striata.com>\n" \
+	"Date: Sun, 13 Apr 2014 18:10:18 +0200\n" \
+	"Subject: [PATCH] Modified binary file\n" \
+	"\n" \
+	"---\n" \
+	" binary.bin | Bin 3 -> 5 bytes\n" \
+	" 1 file changed, 0 insertions(+), 0 deletions(-)\n" \
+	"\n" \
+	"diff --git a/binary.bin b/binary.bin\n" \
+	"index bd474b2519cc15eab801ff851cc7d50f0dee49a1..9ac35ff15cd8864aeafd889e4826a3150f0b06c4 100644\n" \
+	"GIT binary patch\n" \
+	"literal 5\n" \
+	"Mc${NkU}WL~000&M4gdfE\n" \
+	"\n" \
+	"literal 3\n" \
+	"Kc${Nk-~s>u4FC%O\n" \
+	"\n" \
+	"--\n" \
+	"libgit2 " LIBGIT2_VERSION "\n" \
+	"\n";
+
+	assert_email_match(expected, "8d7523f6fcb2404257889abe0d96f093d9f524f9", NULL);
+}
+
+void test_email_create__binary_not_included(void)
+{
+	const char *expected =
+	"From 8d7523f6fcb2404257889abe0d96f093d9f524f9 Mon Sep 17 00:00:00 2001\n" \
+	"From: Jacques Germishuys <jacquesg@striata.com>\n" \
+	"Date: Sun, 13 Apr 2014 18:10:18 +0200\n" \
+	"Subject: [PATCH] Modified binary file\n" \
+	"\n" \
+	"---\n" \
+	" binary.bin | Bin 3 -> 5 bytes\n" \
+	" 1 file changed, 0 insertions(+), 0 deletions(-)\n" \
+	"\n" \
+	"diff --git a/binary.bin b/binary.bin\n" \
+	"index bd474b2..9ac35ff 100644\n" \
+	"Binary files a/binary.bin and b/binary.bin differ\n" \
+	"--\n" \
+	"libgit2 " LIBGIT2_VERSION "\n" \
+	"\n";
+
+	git_email_create_options opts = GIT_EMAIL_CREATE_OPTIONS_INIT;
+	opts.diff_opts.flags &= ~GIT_DIFF_SHOW_BINARY;
+
+	assert_email_match(expected, "8d7523f6fcb2404257889abe0d96f093d9f524f9", &opts);
+}
+
+void test_email_create__custom_summary_and_body(void)
+{
+	const char *expected = "From 627e7e12d87e07a83fad5b6bfa25e86ead4a5270 Mon Sep 17 00:00:00 2001\n" \
+	"From: Patrick Steinhardt <ps@pks.im>\n" \
+	"Date: Tue, 24 Nov 2015 13:34:39 +0100\n" \
+	"Subject: [PPPPPATCH 2/4] This is a subject\n" \
+	"\n" \
+	"Modify content of file3.txt by appending a new line. Make this\n" \
+	"commit message somewhat longer to test behavior with newlines\n" \
+	"embedded in the message body.\n" \
+	"\n" \
+	"Also test if new paragraphs are included correctly.\n" \
+	"---\n" \
+	" file3.txt | 1 +\n" \
+	" 1 file changed, 1 insertion(+)\n" \
+	"\n" \
+	"diff --git a/file3.txt b/file3.txt\n" \
+	"index 9a2d780..7309653 100644\n" \
+	"--- a/file3.txt\n" \
+	"+++ b/file3.txt\n" \
+	"@@ -3,3 +3,4 @@ file3!\n" \
+	" file3\n" \
+	" file3\n" \
+	" file3\n" \
+	"+file3\n" \
+	"--\n" \
+	"libgit2 " LIBGIT2_VERSION "\n" \
+	"\n";
+
+	const char *summary = "This is a subject\nwith\nnewlines";
+	const char *body = "Modify content of file3.txt by appending a new line. Make this\n" \
+	"commit message somewhat longer to test behavior with newlines\n" \
+	"embedded in the message body.\n" \
+	"\n" \
+	"Also test if new paragraphs are included correctly.";
+
+	git_oid oid;
+	git_commit *commit = NULL;
+	git_diff *diff = NULL;
+	git_buf buf = GIT_BUF_INIT;
+	git_email_create_options opts = GIT_EMAIL_CREATE_OPTIONS_INIT;
+
+	opts.subject_prefix = "PPPPPATCH";
+
+	git_oid_fromstr(&oid, "627e7e12d87e07a83fad5b6bfa25e86ead4a5270");
+	cl_git_pass(git_commit_lookup(&commit, repo, &oid));
+	cl_git_pass(git_diff__commit(&diff, repo, commit, NULL));
+	cl_git_pass(git_email_create_from_diff(&buf, diff, 2, 4, &oid, summary, body, git_commit_author(commit), &opts));
+
+	cl_assert_equal_s(expected, git_buf_cstr(&buf));
+
+	git_diff_free(diff);
+	git_commit_free(commit);
+	git_buf_dispose(&buf);
+}
+
+void test_email_create__commit_subjects(void)
+{
+	git_email_create_options opts = GIT_EMAIL_CREATE_OPTIONS_INIT;
+
+	assert_subject_match("[PATCH] Modify some content", "9264b96c6d104d0e07ae33d3007b6a48246c6f92", &opts);
+
+	opts.reroll_number = 42;
+	assert_subject_match("[PATCH v42] Modify some content", "9264b96c6d104d0e07ae33d3007b6a48246c6f92", &opts);
+
+	opts.flags |= GIT_EMAIL_CREATE_ALWAYS_NUMBER;
+	assert_subject_match("[PATCH v42 1/1] Modify some content", "9264b96c6d104d0e07ae33d3007b6a48246c6f92", &opts);
+
+	opts.start_number = 9;
+	assert_subject_match("[PATCH v42 9/9] Modify some content", "9264b96c6d104d0e07ae33d3007b6a48246c6f92", &opts);
+
+	opts.subject_prefix = "";
+	assert_subject_match("[v42 9/9] Modify some content", "9264b96c6d104d0e07ae33d3007b6a48246c6f92", &opts);
+
+	opts.reroll_number = 0;
+	assert_subject_match("[9/9] Modify some content", "9264b96c6d104d0e07ae33d3007b6a48246c6f92", &opts);
+
+	opts.start_number = 0;
+	assert_subject_match("[1/1] Modify some content", "9264b96c6d104d0e07ae33d3007b6a48246c6f92", &opts);
+
+	opts.flags = GIT_EMAIL_CREATE_OMIT_NUMBERS;
+	assert_subject_match("Modify some content", "9264b96c6d104d0e07ae33d3007b6a48246c6f92", &opts);
+}