thodg/libgit2

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 5236a6d..34553aa 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -18,6 +18,12 @@ v0.22 + 1
 * The local transport now auto-scales the number of threads to use
   when creating the packfile instead of sticking to one.
 
+* Reference renaming now uses the right id for the old value.
+
+* The annotated version of branch creation, HEAD detaching and reset
+  allow for specifying the expression from the user to be put into the
+  reflog.
+
 ### API additions
 
 * Parsing and retrieving a configuration value as a path is exposed
@@ -33,7 +39,14 @@ v0.22 + 1
 * `git_config_get_string_buf()` provides a way to safely retrieve a
   string from a non-snapshot configuration.
 
-* Reference renaming now uses the right id for the old value.
+* `git_annotated_commit_from_revspec()` allows to get an annotated
+  commit from an extended sha synatx string.
+
+* `git_repository_set_head_detached_from_annotated()`,
+  `git_branch_create_from_annotated()` and
+  `git_reset_from_annotated()` allow for the caller to provide an
+  annotated commit through which they can control what expression is
+  put into the reflog as the source/target.
 
 * `git_index_add_frombuffer()` can now create a blob from memory
    buffer and add it to the index which is attached to a repository.
diff --git a/include/git2/annotated_commit.h b/include/git2/annotated_commit.h
index e842d20..7fb896a 100644
--- a/include/git2/annotated_commit.h
+++ b/include/git2/annotated_commit.h
@@ -78,6 +78,23 @@ GIT_EXTERN(int) git_annotated_commit_lookup(
 	const git_oid *id);
 
 /**
+ * Creates a `git_annotated_comit` from a revision string.
+ *
+ * See `man gitrevisions`, or
+ * http://git-scm.com/docs/git-rev-parse.html#_specifying_revisions for
+ * information on the syntax accepted.
+ *
+ * @param out pointer to store the git_annotated_commit result in
+ * @param repo repository that contains the given commit
+ * @param revspec the extended sha syntax string to use to lookup the commit
+ * @return 0 on success or error code
+ */
+GIT_EXTERN(int) git_annotated_commit_from_revspec(
+	git_annotated_commit **out,
+	git_repository *repo,
+	const char *revspec);
+
+/**
  * Gets the commit ID that the given `git_annotated_commit` refers to.
  *
  * @param commit the given annotated commit
diff --git a/include/git2/branch.h b/include/git2/branch.h
index 06f4d2c..34354f4 100644
--- a/include/git2/branch.h
+++ b/include/git2/branch.h
@@ -55,6 +55,24 @@ GIT_EXTERN(int) git_branch_create(
 	int force);
 
 /**
+ * Create a new branch pointing at a target commit
+ *
+ * This behaves like `git_branch_create()` but takes an annotated
+ * commit, which lets you specify which extended sha syntax string was
+ * specified by a user, allowing for more exact reflog messages.
+ *
+ * See the documentation for `git_branch_create()`.
+ *
+ * @see git_branch_create
+ */
+GIT_EXTERN(int) git_branch_create_from_annotated(
+	git_reference **ref_out,
+	git_repository *repository,
+	const char *branch_name,
+	const git_annotated_commit *commit,
+	int force);
+
+/**
  * Delete an existing branch reference.
  *
  * If the branch is successfully deleted, the passed reference
diff --git a/include/git2/repository.h b/include/git2/repository.h
index e3ff3b3..ce56fef 100644
--- a/include/git2/repository.h
+++ b/include/git2/repository.h
@@ -630,6 +630,22 @@ GIT_EXTERN(int) git_repository_set_head_detached(
 	const git_oid* commitish);
 
 /**
+ * Make the repository HEAD directly point to the Commit.
+ *
+ * This behaves like `git_repository_set_head_detached()` but takes an
+ * annotated commit, which lets you specify which extended sha syntax
+ * string was specified by a user, allowing for more exact reflog
+ * messages.
+ *
+ * See the documentation for `git_repository_set_head_detached()`.
+ *
+ * @see git_repository_set_head_detached
+ */
+GIT_EXTERN(int) git_repository_set_head_detached_from_annotated(
+	git_repository *repo,
+	const git_annotated_commit *commitish);
+
+/**
  * Detach the HEAD.
  *
  * If the HEAD is already detached and points to a Commit, 0 is returned.
diff --git a/include/git2/reset.h b/include/git2/reset.h
index 93ac0b2..c03dbed 100644
--- a/include/git2/reset.h
+++ b/include/git2/reset.h
@@ -65,6 +65,24 @@ GIT_EXTERN(int) git_reset(
 	git_checkout_options *checkout_opts);
 
 /**
+ * Sets the current head to the specified commit oid and optionally
+ * resets the index and working tree to match.
+ *
+ * This behaves like `git_reset()` but takes an annotated commit,
+ * which lets you specify which extended sha syntax string was
+ * specified by a user, allowing for more exact reflog messages.
+ *
+ * See the documentation for `git_reset()`.
+ *
+ * @see git_reset
+ */
+GIT_EXTERN(int) git_reset_from_annotated(
+	git_repository *repo,
+	git_annotated_commit *commit,
+	git_reset_t reset_type,
+	git_checkout_options *checkout_opts);
+
+/**
  * Updates some entries in the index from the target commit tree.
  *
  * The scope of the updated entries is determined by the paths
diff --git a/src/annotated_commit.c b/src/annotated_commit.c
index 0a91780..3f2d2ed 100644
--- a/src/annotated_commit.c
+++ b/src/annotated_commit.c
@@ -12,6 +12,7 @@
 #include "git2/refs.h"
 #include "git2/repository.h"
 #include "git2/annotated_commit.h"
+#include "git2/revparse.h"
 
 static int annotated_commit_init(
 	git_annotated_commit **out,
@@ -96,6 +97,33 @@ int git_annotated_commit_from_fetchhead(
 	return annotated_commit_init(out, repo, id, branch_name, remote_url);
 }
 
+int git_annotated_commit_from_revspec(
+	git_annotated_commit **out,
+	git_repository *repo,
+	const char *revspec)
+{
+	git_object *obj, *commit;
+	int error;
+
+	assert(out && repo && revspec);
+
+	if ((error = git_revparse_single(&obj, repo, revspec)) < 0)
+		return error;
+
+	if ((error = git_object_peel(&commit, obj, GIT_OBJ_COMMIT))) {
+		git_object_free(obj);
+		return error;
+	}
+
+	error = annotated_commit_init(out, repo, git_object_id(commit), revspec, NULL);
+
+	git_object_free(obj);
+	git_object_free(commit);
+
+	return error;
+}
+
+
 const git_oid *git_annotated_commit_id(
 	const git_annotated_commit *annotated_commit)
 {
diff --git a/src/branch.c b/src/branch.c
index a16d3a3..10be6f7 100644
--- a/src/branch.c
+++ b/src/branch.c
@@ -12,6 +12,7 @@
 #include "refspec.h"
 #include "refs.h"
 #include "remote.h"
+#include "annotated_commit.h"
 
 #include "git2/branch.h"
 
@@ -49,11 +50,12 @@ static int not_a_local_branch(const char *reference_name)
 	return -1;
 }
 
-int git_branch_create(
+static int create_branch(
 	git_reference **ref_out,
 	git_repository *repository,
 	const char *branch_name,
 	const git_commit *commit,
+	const char *from,
 	int force)
 {
 	int is_head = 0;
@@ -86,7 +88,7 @@ int git_branch_create(
 	if (git_buf_joinpath(&canonical_branch_name, GIT_REFS_HEADS_DIR, branch_name) < 0)
 		goto cleanup;
 
-	if (git_buf_printf(&log_message, "branch: Created from %s", git_oid_tostr_s(git_commit_id(commit))) < 0)
+	if (git_buf_printf(&log_message, "branch: Created from %s", from) < 0)
 		goto cleanup;
 
 	error = git_reference_create(&branch, repository,
@@ -102,6 +104,26 @@ cleanup:
 	return error;
 }
 
+int git_branch_create(
+	git_reference **ref_out,
+	git_repository *repository,
+	const char *branch_name,
+	const git_commit *commit,
+	int force)
+{
+	return create_branch(ref_out, repository, branch_name, commit, git_oid_tostr_s(git_commit_id(commit)), force);
+}
+
+int git_branch_create_from_annotated(
+	git_reference **ref_out,
+	git_repository *repository,
+	const char *branch_name,
+	const git_annotated_commit *commit,
+	int force)
+{
+	return create_branch(ref_out, repository, branch_name, commit->commit, commit->ref_name, force);
+}
+
 int git_branch_delete(git_reference *branch)
 {
 	int is_head;
diff --git a/src/repository.c b/src/repository.c
index 0cbdf08..b1f94f0 100644
--- a/src/repository.c
+++ b/src/repository.c
@@ -26,6 +26,7 @@
 #include "remote.h"
 #include "merge.h"
 #include "diff_driver.h"
+#include "annotated_commit.h"
 
 #ifdef GIT_WIN32
 # include "win32/w32_util.h"
@@ -1961,27 +1962,28 @@ cleanup:
 	return error;
 }
 
-int git_repository_set_head_detached(
-	git_repository* repo,
-	const git_oid* commitish)
+static int detach(git_repository *repo, const git_oid *id, const char *from)
 {
 	int error;
 	git_buf log_message = GIT_BUF_INIT;
 	git_object *object = NULL, *peeled = NULL;
 	git_reference *new_head = NULL, *current = NULL;
 
-	assert(repo && commitish);
+	assert(repo && id);
 
 	if ((error = git_reference_lookup(&current, repo, GIT_HEAD_FILE)) < 0)
 		return error;
 
-	if ((error = git_object_lookup(&object, repo, commitish, GIT_OBJ_ANY)) < 0)
+	if ((error = git_object_lookup(&object, repo, id, GIT_OBJ_ANY)) < 0)
 		goto cleanup;
 
 	if ((error = git_object_peel(&peeled, object, GIT_OBJ_COMMIT)) < 0)
 		goto cleanup;
 
-	if ((error = checkout_message(&log_message, current, git_oid_tostr_s(git_object_id(peeled)))) < 0)
+	if (from == NULL)
+		from = git_oid_tostr_s(git_object_id(peeled));
+
+	if ((error = checkout_message(&log_message, current, from)) < 0)
 		goto cleanup;
 
 	error = git_reference_create(&new_head, repo, GIT_HEAD_FILE, git_object_id(peeled), true, git_buf_cstr(&log_message));
@@ -1995,6 +1997,22 @@ cleanup:
 	return error;
 }
 
+int git_repository_set_head_detached(
+	git_repository* repo,
+	const git_oid* commitish)
+{
+	return detach(repo, commitish, NULL);
+}
+
+int git_repository_set_head_detached_from_annotated(
+	git_repository *repo,
+	const git_annotated_commit *commitish)
+{
+	assert(repo && commitish);
+
+	return detach(repo, git_annotated_commit_id(commitish), commitish->ref_name);
+}
+
 int git_repository_detach_head(git_repository* repo)
 {
 	git_reference *old_head = NULL,	*new_head = NULL, *current = NULL;
diff --git a/src/reset.c b/src/reset.c
index 351ecaa..aaebf41 100644
--- a/src/reset.c
+++ b/src/reset.c
@@ -10,6 +10,7 @@
 #include "tag.h"
 #include "merge.h"
 #include "diff.h"
+#include "annotated_commit.h"
 #include "git2/reset.h"
 #include "git2/checkout.h"
 #include "git2/merge.h"
@@ -96,9 +97,10 @@ cleanup:
 	return error;
 }
 
-int git_reset(
+static int reset(
 	git_repository *repo,
 	git_object *target,
+	const char *to,
 	git_reset_t reset_type,
 	git_checkout_options *checkout_opts)
 {
@@ -139,7 +141,7 @@ int git_reset(
 		goto cleanup;
 	}
 
-	if ((error = git_buf_printf(&log_message, "reset: moving to %s", git_oid_tostr_s(git_object_id(commit)))) < 0)
+	if ((error = git_buf_printf(&log_message, "reset: moving to %s", to)) < 0)
 		return error;
 
 	/* move HEAD to the new target */
@@ -176,3 +178,21 @@ cleanup:
 
 	return error;
 }
+
+int git_reset(
+	git_repository *repo,
+	git_object *target,
+	git_reset_t reset_type,
+	git_checkout_options *checkout_opts)
+{
+	return reset(repo, target, git_oid_tostr_s(git_object_id(target)), reset_type, checkout_opts);
+}
+
+int git_reset_from_annotated(
+	git_repository *repo,
+	git_annotated_commit *commit,
+	git_reset_t reset_type,
+	git_checkout_options *checkout_opts)
+{
+	return reset(repo, (git_object *) commit->commit, commit->ref_name, reset_type, checkout_opts);
+}
diff --git a/tests/refs/branches/create.c b/tests/refs/branches/create.c
index d4cf4c2..31dec06 100644
--- a/tests/refs/branches/create.c
+++ b/tests/refs/branches/create.c
@@ -97,6 +97,7 @@ void test_refs_branches_create__default_reflog_message(void)
 	git_reflog *log;
 	git_buf buf = GIT_BUF_INIT;
 	const git_reflog_entry *entry;
+	git_annotated_commit *annotated;
 	git_signature *sig;
 	git_config *cfg;
 
@@ -116,6 +117,21 @@ void test_refs_branches_create__default_reflog_message(void)
 	cl_assert_equal_s(git_buf_cstr(&buf), git_reflog_entry_message(entry));
 	cl_assert_equal_s(sig->email, git_reflog_entry_committer(entry)->email);
 
+	cl_git_pass(git_reference_remove(repo, "refs/heads/" NEW_BRANCH_NAME));
+	git_reference_free(branch);
+	git_reflog_free(log);
+	git_buf_clear(&buf);
+
+	cl_git_pass(git_annotated_commit_from_revspec(&annotated, repo, "e90810b8df3"));
+	cl_git_pass(git_branch_create_from_annotated(&branch, repo, NEW_BRANCH_NAME, annotated, true));
+	cl_git_pass(git_reflog_read(&log, repo, "refs/heads/" NEW_BRANCH_NAME));
+
+	entry = git_reflog_entry_byindex(log, 0);
+	cl_git_pass(git_buf_printf(&buf, "branch: Created from e90810b8df3"));
+	cl_assert_equal_s(git_buf_cstr(&buf), git_reflog_entry_message(entry));
+	cl_assert_equal_s(sig->email, git_reflog_entry_committer(entry)->email);
+
+	git_annotated_commit_free(annotated);
 	git_buf_free(&buf);
 	git_reflog_free(log);
 	git_signature_free(sig);
diff --git a/tests/repo/head.c b/tests/repo/head.c
index b26d6ac..31c2287 100644
--- a/tests/repo/head.c
+++ b/tests/repo/head.c
@@ -2,6 +2,7 @@
 #include "refs.h"
 #include "repo_helpers.h"
 #include "posix.h"
+#include "git2/annotated_commit.h"
 
 static const char *g_email = "foo@example.com";
 static git_repository *repo;
@@ -251,6 +252,7 @@ void test_repo_head__setting_head_updates_reflog(void)
 {
 	git_object *tag;
 	git_signature *sig;
+	git_annotated_commit *annotated;
 
 	cl_git_pass(git_signature_now(&sig, "me", "foo@example.com"));
 
@@ -264,6 +266,12 @@ void test_repo_head__setting_head_updates_reflog(void)
 	test_reflog(repo, 1, NULL, "tags/test^{commit}", "foo@example.com", "checkout: moving from unborn to e90810b8df3e80c413d903f631643c716887138d");
 	test_reflog(repo, 0, "tags/test^{commit}", "refs/heads/haacked", "foo@example.com", "checkout: moving from e90810b8df3e80c413d903f631643c716887138d to haacked");
 
+	cl_git_pass(git_annotated_commit_from_revspec(&annotated, repo, "haacked~0"));
+	cl_git_pass(git_repository_set_head_detached_from_annotated(repo, annotated));
+
+	test_reflog(repo, 0, NULL, "refs/heads/haacked", "foo@example.com", "checkout: moving from haacked to haacked~0");
+
+	git_annotated_commit_free(annotated);
 	git_object_free(tag);
 	git_signature_free(sig);
 }
diff --git a/tests/reset/hard.c b/tests/reset/hard.c
index f6ca103..86d4be2 100644
--- a/tests/reset/hard.c
+++ b/tests/reset/hard.c
@@ -201,6 +201,7 @@ void test_reset_hard__cleans_up_merge(void)
 void test_reset_hard__reflog_is_correct(void)
 {
 	git_buf buf = GIT_BUF_INIT;
+	git_annotated_commit *annotated;
 	const char *exp_msg = "commit: Add a file which name should appear before the "
 		"\"subdir/\" folder while being dealt with by the treewalker";
 
@@ -215,7 +216,7 @@ void test_reset_hard__reflog_is_correct(void)
 
 	git_object_free(target);
 
-	/* Moved branch, expect default message */
+	/* Moved branch, expect id in message */
 	cl_git_pass(git_revparse_single(&target, repo, "HEAD~^{commit}"));
 	cl_git_pass(git_buf_printf(&buf, "reset: moving to %s", git_oid_tostr_s(git_object_id(target))));
 	cl_git_pass(git_reset(repo, target, GIT_RESET_HARD, NULL));
@@ -223,4 +224,14 @@ void test_reset_hard__reflog_is_correct(void)
 	reflog_check(repo, "refs/heads/master", 4, NULL, git_buf_cstr(&buf));
 
 	git_buf_free(&buf);
+
+	/* Moved branch, expect revspec in message */
+	exp_msg = "reset: moving to HEAD~^{commit}";
+	cl_git_pass(git_annotated_commit_from_revspec(&annotated, repo, "HEAD~^{commit}"));
+	cl_git_pass(git_reset_from_annotated(repo, annotated, GIT_RESET_HARD, NULL));
+	reflog_check(repo, "HEAD", 5, NULL, exp_msg);
+	reflog_check(repo, "refs/heads/master", 5, NULL, exp_msg);
+
+	git_annotated_commit_free(annotated);
+
 }
diff --git a/tests/reset/mixed.c b/tests/reset/mixed.c
index b374902..97eac74 100644
--- a/tests/reset/mixed.c
+++ b/tests/reset/mixed.c
@@ -51,6 +51,7 @@ void test_reset_mixed__resetting_refreshes_the_index_to_the_commit_tree(void)
 void test_reset_mixed__reflog_is_correct(void)
 {
 	git_buf buf = GIT_BUF_INIT;
+	git_annotated_commit *annotated;
 	const char *exp_msg = "commit: Updating test data so we can test inter-hunk-context";
 
 	reflog_check(repo, "HEAD", 9, "yoram.harmelin@gmail.com", exp_msg);
@@ -65,13 +66,20 @@ void test_reset_mixed__reflog_is_correct(void)
 	git_object_free(target);
 	target = NULL;
 
-	/* Moved branch, expect default message */
+	/* Moved branch, expect id in message */
 	cl_git_pass(git_revparse_single(&target, repo, "HEAD~^{commit}"));
 	git_buf_clear(&buf);
 	cl_git_pass(git_buf_printf(&buf, "reset: moving to %s", git_oid_tostr_s(git_object_id(target))));
 	cl_git_pass(git_reset(repo, target, GIT_RESET_MIXED, NULL));
 	reflog_check(repo, "HEAD", 10, NULL, git_buf_cstr(&buf));
 	reflog_check(repo, "refs/heads/master", 10, NULL, git_buf_cstr(&buf));
-
 	git_buf_free(&buf);
+
+	/* Moved branch, expect revspec in message */
+	exp_msg = "reset: moving to HEAD~^{commit}";
+	cl_git_pass(git_annotated_commit_from_revspec(&annotated, repo, "HEAD~^{commit}"));
+	cl_git_pass(git_reset_from_annotated(repo, annotated, GIT_RESET_MIXED, NULL));
+	reflog_check(repo, "HEAD", 11, NULL, exp_msg);
+	reflog_check(repo, "refs/heads/master", 11, NULL, exp_msg);
+	git_annotated_commit_free(annotated);
 }
diff --git a/tests/reset/soft.c b/tests/reset/soft.c
index a5bb13c..506deca 100644
--- a/tests/reset/soft.c
+++ b/tests/reset/soft.c
@@ -155,28 +155,35 @@ void test_reset_soft__fails_when_index_contains_conflicts_independently_of_MERGE
 	cl_assert_equal_i(GIT_EUNMERGED, git_reset(repo, target, GIT_RESET_SOFT, NULL));
 }
 
-void test_reset_soft_reflog_is_correct(void)
+void test_reset_soft__reflog_is_correct(void)
 {
-	const char *exp_msg = "commit: Updating test data so we can test inter-hunk-context";
+	git_annotated_commit *annotated;
+	const char *exp_msg = "checkout: moving from br2 to master";
+	const char *master_msg = "commit: checking in";
 
-	reflog_check(repo, "HEAD", 9, "yoram.harmelin@gmail.com", exp_msg);
-	reflog_check(repo, "refs/heads/master", 9, "yoram.harmelin@gmail.com", exp_msg);
+	reflog_check(repo, "HEAD", 7, "yoram.harmelin@gmail.com", exp_msg);
+	reflog_check(repo, "refs/heads/master", 2, "yoram.harmelin@gmail.com", master_msg);
 
 	/* Branch not moving, no reflog entry */
 	cl_git_pass(git_revparse_single(&target, repo, "HEAD^{commit}"));
 	cl_git_pass(git_reset(repo, target, GIT_RESET_SOFT, NULL));
-	reflog_check(repo, "HEAD", 9, "yoram.harmelin@gmail.com", exp_msg);
-	reflog_check(repo, "refs/heads/master", 9, "yoram.harmelin@gmail.com", exp_msg);
+	reflog_check(repo, "HEAD", 7, "yoram.harmelin@gmail.com", exp_msg);
+	reflog_check(repo, "refs/heads/master", 2, "yoram.harmelin@gmail.com", master_msg);
+	git_object_free(target);
 
-	/* Moved branch, expect default message */
+	/* Moved branch, expect id in message */
+	exp_msg = "reset: moving to be3563ae3f795b2b4353bcce3a527ad0a4f7f644";
 	cl_git_pass(git_revparse_single(&target, repo, "HEAD~^{commit}"));
 	cl_git_pass(git_reset(repo, target, GIT_RESET_SOFT, NULL));
-	reflog_check(repo, "HEAD", 9, "yoram.harmelin@gmail.com", exp_msg);
-	reflog_check(repo, "refs/heads/master", 10, NULL, "reset: moving");
+	reflog_check(repo, "HEAD", 8, "yoram.harmelin@gmail.com", exp_msg);
+	reflog_check(repo, "refs/heads/master", 3, NULL, exp_msg);
 
-	/* Moved branch, expect custom message */
-	cl_git_pass(git_revparse_single(&target, repo, "HEAD~^{commit}"));
-	cl_git_pass(git_reset(repo, target, GIT_RESET_SOFT, NULL));
+	/* Moved branch, expect message with annotated string */
+	exp_msg = "reset: moving to HEAD~^{commit}";
+	cl_git_pass(git_annotated_commit_from_revspec(&annotated, repo, "HEAD~^{commit}"));
+	cl_git_pass(git_reset_from_annotated(repo, annotated, GIT_RESET_SOFT, NULL));
 	reflog_check(repo, "HEAD", 9, "yoram.harmelin@gmail.com", exp_msg);
-	reflog_check(repo, "refs/heads/master", 11, NULL, "message1");
+	reflog_check(repo, "refs/heads/master", 4, NULL, exp_msg);
+
+	git_annotated_commit_free(annotated);
 }