thodg/libgit2

diff --git a/src/blob.c b/src/blob.c
index 3ff141c..c0514fc 100644
--- a/src/blob.c
+++ b/src/blob.c
@@ -12,6 +12,7 @@
 #include "common.h"
 #include "blob.h"
 #include "filter.h"
+#include "buf_text.h"
 
 const void *git_blob_rawcontent(const git_blob *blob)
 {
diff --git a/src/buf_text.c b/src/buf_text.c
index 3a8f442..443454b 100644
--- a/src/buf_text.c
+++ b/src/buf_text.c
@@ -60,6 +60,83 @@ void git_buf_text_unescape(git_buf *buf)
 	buf->size = git__unescape(buf->ptr);
 }
 
+int git_buf_text_crlf_to_lf(git_buf *tgt, const git_buf *src)
+{
+	const char *scan = src->ptr;
+	const char *scan_end = src->ptr + src->size;
+	const char *next = memchr(scan, '\r', src->size);
+	char *out;
+
+	assert(tgt != src);
+
+	if (!next)
+		return GIT_ENOTFOUND;
+
+	/* reduce reallocs while in the loop */
+	if (git_buf_grow(tgt, src->size) < 0)
+		return -1;
+	out = tgt->ptr;
+	tgt->size = 0;
+
+	/* Find the next \r and copy whole chunk up to there to tgt */
+	for (; next; scan = next + 1, next = memchr(scan, '\r', scan_end - scan)) {
+		if (next > scan) {
+			size_t copylen = next - scan;
+			memcpy(out, scan, copylen);
+			out += copylen;
+		}
+
+		/* Do not drop \r unless it is followed by \n */
+		if (next[1] != '\n')
+			*out++ = '\r';
+	}
+
+	/* Copy remaining input into dest */
+	memcpy(out, scan, scan_end - scan + 1); /* +1 for NUL byte */
+	out += (scan_end - scan);
+	tgt->size = out - tgt->ptr;
+
+	return 0;
+}
+
+int git_buf_text_lf_to_crlf(git_buf *tgt, const git_buf *src)
+{
+	const char *start = src->ptr;
+	const char *end = start + src->size;
+	const char *scan = start;
+	const char *next = memchr(scan, '\n', src->size);
+
+	assert(tgt != src);
+
+	if (!next)
+		return GIT_ENOTFOUND;
+
+	/* attempt to reduce reallocs while in the loop */
+	if (git_buf_grow(tgt, src->size + (src->size >> 4) + 1) < 0)
+		return -1;
+	tgt->size = 0;
+
+	for (; next; scan = next + 1, next = memchr(scan, '\n', end - scan)) {
+		size_t copylen = next - scan;
+		/* don't convert existing \r\n to \r\r\n */
+		size_t extralen = (next > start && next[-1] == '\r') ? 1 : 2;
+		size_t needsize = tgt->size + copylen + extralen + 1;
+
+		if (tgt->asize < needsize && git_buf_grow(tgt, needsize) < 0)
+			return -1;
+
+		if (next > scan) {
+			memcpy(tgt->ptr + tgt->size, scan, copylen);
+			tgt->size += copylen;
+		}
+		if (extralen == 2)
+			tgt->ptr[tgt->size++] = '\r';
+		tgt->ptr[tgt->size++] = '\n';
+	}
+
+	return git_buf_put(tgt, scan, end - scan);
+}
+
 int git_buf_text_common_prefix(git_buf *buf, const git_strarray *strings)
 {
 	size_t i;
diff --git a/src/buf_text.h b/src/buf_text.h
index 458ee33..58e4e26 100644
--- a/src/buf_text.h
+++ b/src/buf_text.h
@@ -56,6 +56,20 @@ GIT_INLINE(int) git_buf_text_puts_escape_regex(git_buf *buf, const char *string)
 extern void git_buf_text_unescape(git_buf *buf);
 
 /**
+ * Replace all \r\n with \n (or do nothing if no \r\n are found)
+ *
+ * @return 0 on success, GIT_ENOTFOUND if no \r\n, -1 on memory error
+ */
+extern int git_buf_text_crlf_to_lf(git_buf *tgt, const git_buf *src);
+
+/**
+ * Replace all \n with \r\n (or do nothing if no \n are found)
+ *
+ * @return 0 on success, GIT_ENOTFOUND if no \n, -1 on memory error
+ */
+extern int git_buf_text_lf_to_crlf(git_buf *tgt, const git_buf *src);
+
+/**
  * Fill buffer with the common prefix of a array of strings
  *
  * Buffer will be set to empty if there is no common prefix
diff --git a/src/checkout.c b/src/checkout.c
index e52649a..5a2698e 100644
--- a/src/checkout.c
+++ b/src/checkout.c
@@ -23,6 +23,7 @@
 #include "blob.h"
 #include "diff.h"
 #include "pathspec.h"
+#include "buf_text.h"
 
 /* See docs/checkout-internals.md for more information */
 
diff --git a/src/crlf.c b/src/crlf.c
index cd6d982..81268da 100644
--- a/src/crlf.c
+++ b/src/crlf.c
@@ -9,6 +9,7 @@
 #include "fileops.h"
 #include "hash.h"
 #include "filter.h"
+#include "buf_text.h"
 #include "repository.h"
 #include "git2/attr.h"
 #include "git2/blob.h"
@@ -105,35 +106,6 @@ static int crlf_load_attributes(struct crlf_attrs *ca, git_repository *repo, con
 	return -1;
 }
 
-static int drop_crlf(git_buf *dest, const git_buf *source)
-{
-	const char *scan = source->ptr, *next;
-	const char *scan_end = git_buf_cstr(source) + git_buf_len(source);
-
-	/* Main scan loop.  Find the next carriage return and copy the
-	 * whole chunk up to that point to the destination buffer.
-	 */
-	while ((next = memchr(scan, '\r', scan_end - scan)) != NULL) {
-		/* copy input up to \r */
-		if (next > scan)
-			git_buf_put(dest, scan, next - scan);
-
-		/* Do not drop \r unless it is followed by \n */
-		if (*(next + 1) != '\n')
-			git_buf_putc(dest, '\r');
-
-		scan = next + 1;
-	}
-
-	/* If there was no \r, then tell the library to skip this filter */
-	if (scan == source->ptr)
-		return -1;
-
-	/* Copy remaining input into dest */
-	git_buf_put(dest, scan, scan_end - scan);
-	return 0;
-}
-
 static int has_cr_in_index(git_filter *self)
 {
 	struct crlf_filter *filter = (struct crlf_filter *)self;
@@ -217,29 +189,7 @@ static int crlf_apply_to_odb(
 	}
 
 	/* Actually drop the carriage returns */
-	return drop_crlf(dest, source);
-}
-
-static int convert_line_endings(git_buf *dest, const git_buf *source, const char *ending)
-{
-	const char *scan = git_buf_cstr(source),
-		*next,
-		*line_end,
-		*scan_end = git_buf_cstr(source) + git_buf_len(source);
-
-	while ((next = memchr(scan, '\n', scan_end - scan)) != NULL) {
-		if (next > scan) {
-			line_end = *(next - 1) == '\r' ? next - 1 : next;
-			git_buf_put(dest, scan, line_end - scan);
-			scan = next + 1;
-		}
-
-		git_buf_puts(dest, ending);
-		scan = next + 1;
-	}
-
-	git_buf_put(dest, scan, scan_end - scan);
-	return 0;
+	return git_buf_text_crlf_to_lf(dest, source);
 }
 
 static const char *line_ending(struct crlf_filter *filter)
@@ -282,26 +232,28 @@ line_ending_error:
 	return NULL;
 }
 
-static int crlf_apply_to_workdir(git_filter *self, git_buf *dest, const git_buf *source)
+static int crlf_apply_to_workdir(
+	git_filter *self, git_buf *dest, const git_buf *source)
 {
 	struct crlf_filter *filter = (struct crlf_filter *)self;
 	const char *workdir_ending = NULL;
 
-	assert (self && dest && source);
+	assert(self && dest && source);
 
 	/* Empty file? Nothing to do. */
 	if (git_buf_len(source) == 0)
-		return 0;
+		return -1;
 
 	/* Determine proper line ending */
 	workdir_ending = line_ending(filter);
-	if (!workdir_ending) return -1;
-
-	/* If the line ending is '\n', just copy the input */
-	if (!strcmp(workdir_ending, "\n"))
-		return git_buf_puts(dest, git_buf_cstr(source));
+	if (!workdir_ending)
+		return -1;
+	if (!strcmp("\n", workdir_ending)) /* do nothing for \n ending */
+		return -1;
 
-	return convert_line_endings(dest, source, workdir_ending);
+	/* for now, only lf->crlf conversion is supported here */
+	assert(!strcmp("\r\n", workdir_ending));
+	return git_buf_text_lf_to_crlf(dest, source);
 }
 
 static int find_and_add_filter(
@@ -351,12 +303,14 @@ static int find_and_add_filter(
 	return git_vector_insert(filters, filter);
 }
 
-int git_filter_add__crlf_to_odb(git_vector *filters, git_repository *repo, const char *path)
+int git_filter_add__crlf_to_odb(
+	git_vector *filters, git_repository *repo, const char *path)
 {
 	return find_and_add_filter(filters, repo, path, &crlf_apply_to_odb);
 }
 
-int git_filter_add__crlf_to_workdir(git_vector *filters, git_repository *repo, const char *path)
+int git_filter_add__crlf_to_workdir(
+	git_vector *filters, git_repository *repo, const char *path)
 {
 	return find_and_add_filter(filters, repo, path, &crlf_apply_to_workdir);
 }
diff --git a/src/diff_output.c b/src/diff_output.c
index fba6129..e8dd5b3 100644
--- a/src/diff_output.c
+++ b/src/diff_output.c
@@ -12,6 +12,7 @@
 #include <ctype.h>
 #include "fileops.h"
 #include "filter.h"
+#include "buf_text.h"
 
 static int read_next_int(const char **str, int *value)
 {
diff --git a/src/filter.h b/src/filter.h
index 0ca7165..42a44eb 100644
--- a/src/filter.h
+++ b/src/filter.h
@@ -9,7 +9,6 @@
 
 #include "common.h"
 #include "buffer.h"
-#include "buf_text.h"
 #include "git2/odb.h"
 #include "git2/repository.h"
 
diff --git a/tests-clar/core/buffer.c b/tests-clar/core/buffer.c
index cb5f016..3d8221e 100644
--- a/tests-clar/core/buffer.c
+++ b/tests-clar/core/buffer.c
@@ -904,3 +904,85 @@ void test_core_buffer__similarity_metric_whitespace(void)
 
 	git_buf_free(&buf);
 }
+
+#define check_buf(expected,buf) do { \
+	cl_assert_equal_s(expected, buf.ptr); \
+	cl_assert_equal_sz(strlen(expected), buf.size); } while (0)
+
+void test_core_buffer__lf_and_crlf_conversions(void)
+{
+	git_buf src = GIT_BUF_INIT, tgt = GIT_BUF_INIT;
+
+	/* LF source */
+
+	git_buf_sets(&src, "lf\nlf\nlf\nlf\n");
+
+	cl_git_pass(git_buf_text_lf_to_crlf(&tgt, &src));
+	check_buf("lf\r\nlf\r\nlf\r\nlf\r\n", tgt);
+
+	cl_assert_equal_i(GIT_ENOTFOUND, git_buf_text_crlf_to_lf(&tgt, &src));
+	/* no conversion needed if all LFs already */
+
+	git_buf_sets(&src, "\nlf\nlf\nlf\nlf\nlf");
+
+	cl_git_pass(git_buf_text_lf_to_crlf(&tgt, &src));
+	check_buf("\r\nlf\r\nlf\r\nlf\r\nlf\r\nlf", tgt);
+
+	cl_assert_equal_i(GIT_ENOTFOUND, git_buf_text_crlf_to_lf(&tgt, &src));
+	/* no conversion needed if all LFs already */
+
+	/* CRLF source */
+
+	git_buf_sets(&src, "crlf\r\ncrlf\r\ncrlf\r\ncrlf\r\n");
+
+	cl_git_pass(git_buf_text_lf_to_crlf(&tgt, &src));
+	check_buf("crlf\r\ncrlf\r\ncrlf\r\ncrlf\r\n", tgt);
+	check_buf(src.ptr, tgt);
+
+	cl_git_pass(git_buf_text_crlf_to_lf(&tgt, &src));
+	check_buf("crlf\ncrlf\ncrlf\ncrlf\n", tgt);
+
+	git_buf_sets(&src, "\r\ncrlf\r\ncrlf\r\ncrlf\r\ncrlf\r\ncrlf");
+
+	cl_git_pass(git_buf_text_lf_to_crlf(&tgt, &src));
+	check_buf("\r\ncrlf\r\ncrlf\r\ncrlf\r\ncrlf\r\ncrlf", tgt);
+	check_buf(src.ptr, tgt);
+
+	cl_git_pass(git_buf_text_crlf_to_lf(&tgt, &src));
+	check_buf("\ncrlf\ncrlf\ncrlf\ncrlf\ncrlf", tgt);
+
+	/* CRLF in LF text */
+
+	git_buf_sets(&src, "\nlf\nlf\ncrlf\r\nlf\nlf\ncrlf\r\n");
+
+	cl_git_pass(git_buf_text_lf_to_crlf(&tgt, &src));
+	check_buf("\r\nlf\r\nlf\r\ncrlf\r\nlf\r\nlf\r\ncrlf\r\n", tgt);
+	cl_git_pass(git_buf_text_crlf_to_lf(&tgt, &src));
+	check_buf("\nlf\nlf\ncrlf\nlf\nlf\ncrlf\n", tgt);
+
+	/* LF in CRLF text */
+
+	git_buf_sets(&src, "\ncrlf\r\ncrlf\r\nlf\ncrlf\r\ncrlf");
+
+	cl_git_pass(git_buf_text_lf_to_crlf(&tgt, &src));
+	check_buf("\r\ncrlf\r\ncrlf\r\nlf\r\ncrlf\r\ncrlf", tgt);
+	cl_git_pass(git_buf_text_crlf_to_lf(&tgt, &src));
+	check_buf("\ncrlf\ncrlf\nlf\ncrlf\ncrlf", tgt);
+
+	/* bare CR test */
+
+	git_buf_sets(&src, "\rcrlf\r\nlf\nlf\ncr\rcrlf\r\nlf\ncr\r");
+
+	cl_git_pass(git_buf_text_lf_to_crlf(&tgt, &src));
+	check_buf("\rcrlf\r\nlf\r\nlf\r\ncr\rcrlf\r\nlf\r\ncr\r", tgt);
+	cl_git_pass(git_buf_text_crlf_to_lf(&tgt, &src));
+	check_buf("\rcrlf\nlf\nlf\ncr\rcrlf\nlf\ncr\r", tgt);
+
+	git_buf_sets(&src, "\rcr\r");
+	cl_assert_equal_i(GIT_ENOTFOUND, git_buf_text_lf_to_crlf(&tgt, &src));
+	cl_git_pass(git_buf_text_crlf_to_lf(&tgt, &src));
+	check_buf("\rcr\r", tgt);
+
+	git_buf_free(&src);
+	git_buf_free(&tgt);
+}
diff --git a/tests-clar/object/blob/filter.c b/tests-clar/object/blob/filter.c
index b9bbfff..042bdda 100644
--- a/tests-clar/object/blob/filter.c
+++ b/tests-clar/object/blob/filter.c
@@ -2,6 +2,7 @@
 #include "posix.h"
 #include "blob.h"
 #include "filter.h"
+#include "buf_text.h"
 
 static git_repository *g_repo = NULL;
 #define NUM_TEST_OBJECTS 8