thodg/libgit2

diff --git a/src/revparse.c b/src/revparse.c
index 05ee1c5..8848799 100644
--- a/src/revparse.c
+++ b/src/revparse.c
@@ -67,10 +67,9 @@ cleanup:
 	return error;
 }
 
-static int maybe_sha_or_abbrev(git_object**out, git_repository *repo, const char *spec)
+static int maybe_sha_or_abbrev(git_object** out, git_repository *repo, const char *spec, size_t speclen)
 {
 	git_oid oid;
-	size_t speclen = strlen(spec);
 
 	if (git_oid_fromstrn(&oid, spec, speclen) < 0)
 		return GIT_ENOTFOUND;
@@ -78,6 +77,23 @@ static int maybe_sha_or_abbrev(git_object**out, git_repository *repo, const char
 	return git_object_lookup_prefix(out, repo, &oid, speclen, GIT_OBJ_ANY);
 }
 
+static int maybe_sha(git_object** out, git_repository *repo, const char *spec)
+{
+	size_t speclen = strlen(spec);
+
+	if (speclen != GIT_OID_HEXSZ)
+		return GIT_ENOTFOUND;
+
+	return maybe_sha_or_abbrev(out, repo, spec, speclen);
+}
+
+static int maybe_abbrev(git_object** out, git_repository *repo, const char *spec)
+{
+	size_t speclen = strlen(spec);
+
+	return maybe_sha_or_abbrev(out, repo, spec, speclen);
+}
+
 static int build_regex(regex_t *regex, const char *pattern)
 {
 	int error;
@@ -118,7 +134,7 @@ static int maybe_describe(git_object**out, git_repository *repo, const char *spe
 	if (error)
 		return GIT_ENOTFOUND;
 
-	return maybe_sha_or_abbrev(out, repo, substr+2);
+	return maybe_abbrev(out, repo, substr+2);
 }
 
 static int revparse_lookup_object(git_object **out, git_repository *repo, const char *spec)
@@ -126,7 +142,7 @@ static int revparse_lookup_object(git_object **out, git_repository *repo, const 
 	int error;
 	git_reference *ref;
 
-	error = maybe_describe(out, repo, spec);
+	error = maybe_sha(out, repo, spec);
 	if (!error)
 		return 0;
 
@@ -143,7 +159,14 @@ static int revparse_lookup_object(git_object **out, git_repository *repo, const 
 	if (error < 0 && error != GIT_ENOTFOUND)
 		return error;
 
-	error = maybe_sha_or_abbrev(out, repo, spec);
+	error = maybe_abbrev(out, repo, spec);
+	if (!error)
+		return 0;
+
+	if (error < 0 && error != GIT_ENOTFOUND)
+		return error;
+
+	error = maybe_describe(out, repo, spec);
 	if (!error)
 		return 0;
 
@@ -217,7 +240,7 @@ static int retrieve_previously_checked_out_branch_or_revision(git_object **out, 
 		if (error < 0 && error != GIT_ENOTFOUND)
 			goto cleanup;
 
-		error = maybe_sha_or_abbrev(out, repo, git_buf_cstr(&buf));
+		error = maybe_abbrev(out, repo, git_buf_cstr(&buf));
 
 		goto cleanup;
 	}
diff --git a/tests-clar/refs/revparse.c b/tests-clar/refs/revparse.c
index 81a6bc4..be92c19 100644
--- a/tests-clar/refs/revparse.c
+++ b/tests-clar/refs/revparse.c
@@ -486,3 +486,112 @@ void test_refs_revparse__issue_994(void)
 	git_reference_free(head);
 	cl_git_sandbox_cleanup();
 }
+
+/**
+ * $ git rev-parse blah-7-gc47800c
+ * c47800c7266a2be04c571c04d5a6614691ea99bd
+ * 
+ * $ git rev-parse HEAD~3
+ * 4a202b346bb0fb0db7eff3cffeb3c70babbd2045
+ * 
+ * $ git branch blah-7-gc47800c HEAD~3
+ * 
+ * $ git rev-parse blah-7-gc47800c
+ * 4a202b346bb0fb0db7eff3cffeb3c70babbd2045
+ */
+void test_refs_revparse__try_to_retrieve_branch_before_described_tag(void)
+{
+	git_repository *repo;
+	git_reference *branch;
+	git_object *target;
+	char sha[GIT_OID_HEXSZ + 1];
+
+	repo = cl_git_sandbox_init("testrepo.git");
+
+	test_object_inrepo("blah-7-gc47800c", "c47800c7266a2be04c571c04d5a6614691ea99bd", repo);
+
+	cl_git_pass(git_revparse_single(&target, repo, "HEAD~3"));
+	cl_git_pass(git_branch_create(&branch, repo, "blah-7-gc47800c", (git_commit *)target, 0));
+
+	git_oid_tostr(sha, GIT_OID_HEXSZ + 1, git_object_id(target));
+
+	test_object_inrepo("blah-7-gc47800c", sha, repo);
+
+	git_reference_free(branch);
+	git_object_free(target);
+	cl_git_sandbox_cleanup();
+}
+
+/**
+ * $ git rev-parse a65fedf39aefe402d3bb6e24df4d4f5fe4547750
+ * a65fedf39aefe402d3bb6e24df4d4f5fe4547750
+ * 
+ * $ git rev-parse HEAD~3
+ * 4a202b346bb0fb0db7eff3cffeb3c70babbd2045
+ * 
+ * $ git branch a65fedf39aefe402d3bb6e24df4d4f5fe4547750 HEAD~3
+ * 
+ * $ git rev-parse a65fedf39aefe402d3bb6e24df4d4f5fe4547750
+ * a65fedf39aefe402d3bb6e24df4d4f5fe4547750
+ * 
+ * $ git rev-parse heads/a65fedf39aefe402d3bb6e24df4d4f5fe4547750
+ * 4a202b346bb0fb0db7eff3cffeb3c70babbd2045
+ */
+void test_refs_revparse__try_to_retrieve_sha_before_branch(void)
+{
+	git_repository *repo;
+	git_reference *branch;
+	git_object *target;
+	char sha[GIT_OID_HEXSZ + 1];
+
+	repo = cl_git_sandbox_init("testrepo.git");
+
+	test_object_inrepo("a65fedf39aefe402d3bb6e24df4d4f5fe4547750", "a65fedf39aefe402d3bb6e24df4d4f5fe4547750", repo);
+
+	cl_git_pass(git_revparse_single(&target, repo, "HEAD~3"));
+	cl_git_pass(git_branch_create(&branch, repo, "a65fedf39aefe402d3bb6e24df4d4f5fe4547750", (git_commit *)target, 0));
+
+	git_oid_tostr(sha, GIT_OID_HEXSZ + 1, git_object_id(target));
+
+	test_object_inrepo("a65fedf39aefe402d3bb6e24df4d4f5fe4547750", "a65fedf39aefe402d3bb6e24df4d4f5fe4547750", repo);
+	test_object_inrepo("heads/a65fedf39aefe402d3bb6e24df4d4f5fe4547750", sha, repo);
+
+	git_reference_free(branch);
+	git_object_free(target);
+	cl_git_sandbox_cleanup();
+}
+
+/**
+ * $ git rev-parse c47800
+ * c47800c7266a2be04c571c04d5a6614691ea99bd
+ * 
+ * $ git rev-parse HEAD~3
+ * 4a202b346bb0fb0db7eff3cffeb3c70babbd2045
+ * 
+ * $ git branch c47800 HEAD~3
+ * 
+ * $ git rev-parse c47800
+ * 4a202b346bb0fb0db7eff3cffeb3c70babbd2045
+ */
+void test_refs_revparse__try_to_retrieve_branch_before_abbrev_sha(void)
+{
+	git_repository *repo;
+	git_reference *branch;
+	git_object *target;
+	char sha[GIT_OID_HEXSZ + 1];
+
+	repo = cl_git_sandbox_init("testrepo.git");
+
+	test_object_inrepo("c47800", "c47800c7266a2be04c571c04d5a6614691ea99bd", repo);
+
+	cl_git_pass(git_revparse_single(&target, repo, "HEAD~3"));
+	cl_git_pass(git_branch_create(&branch, repo, "c47800", (git_commit *)target, 0));
+
+	git_oid_tostr(sha, GIT_OID_HEXSZ + 1, git_object_id(target));
+
+	test_object_inrepo("c47800", sha, repo);
+
+	git_reference_free(branch);
+	git_object_free(target);
+	cl_git_sandbox_cleanup();
+}