[PATCH] commit: skip discarding the index if there is no pre-commit hook

[Kevin Willford <kcwillford@gmail.com>]

If there is not a pre-commit hook, there is no reason to discard
the index and reread it.

This change checks to presence of a pre-commit hook and then only
discards the index if there was one.

Signed-off-by: Kevin Willford <kewillf@microsoft.com>
---
 builtin/commit.c | 29 +++++++++++++++++++++--------
 1 file changed, 21 insertions(+), 8 deletions(-)

diff --git a/builtin/commit.c b/builtin/commit.c
index e7a2cb6285..443949d87b 100644
--- a/builtin/commit.c
+++ b/builtin/commit.c
@@ -671,12 +671,22 @@ static int prepare_to_commit(const char *index_file, const char *prefix,
 	const char *hook_arg2 = NULL;
 	int clean_message_contents = (cleanup_mode != CLEANUP_NONE);
 	int old_display_comment_prefix;
+	const char *precommit_hook = NULL;
 
 	/* This checks and barfs if author is badly specified */
 	determine_author_info(author_ident);
 
-	if (!no_verify && run_commit_hook(use_editor, index_file, "pre-commit", NULL))
-		return 0;
+
+	if (!no_verify) {
+		/*
+		 * Check to see if there is a pre-commit hook
+		 * If there not one we can skip discarding the index later on
+		 */
+		precommit_hook = find_hook("pre-commit");
+		if (precommit_hook &&
+		    run_commit_hook(use_editor, index_file, "pre-commit", NULL))
+			return 0;
+	}
 
 	if (squash_message) {
 		/*
@@ -940,12 +950,15 @@ static int prepare_to_commit(const char *index_file, const char *prefix,
 		return 0;
 	}
 
-	/*
-	 * Re-read the index as pre-commit hook could have updated it,
-	 * and write it out as a tree.  We must do this before we invoke
-	 * the editor and after we invoke run_status above.
-	 */
-	discard_cache();
+	if (!no_verify && precommit_hook) {
+		/*
+		 * Re-read the index as pre-commit hook could have updated it,
+		 * and write it out as a tree.  We must do this before we invoke
+		 * the editor and after we invoke run_status above.
+		 */
+		discard_cache();
+	}
+
 	read_cache_from(index_file);
 	if (update_main_cache_tree(0)) {
 		error(_("Error building trees"));
-- 
2.14.0.rc0.286.g44127d70e4