commit: add --cleanup=scissors

Since 1a72cfd (commit -v: strip diffs and submodule shortlogs from the
commit message - 2013-12-05) we have a less fragile way to cut out
"git status" at the end of a commit message but it's only enabled for
stripping submodule shortlogs.

Add new cleanup option that reuses the same mechanism for the entire
"git status" without accidentally removing lines starting with '#'.

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/git-commit.txt

@@ -176,7 +176,7 @@ OPTIONS
 --cleanup=<mode>::
 	This option determines how the supplied commit message should be
 	cleaned up before committing.  The '<mode>' can be `strip`,
-	`whitespace`, `verbatim`, or `default`.
+	`whitespace`, `verbatim`, `scissors` or `default`.
 +
 --
 strip::
@@ -186,6 +186,12 @@ whitespace::
 	Same as `strip` except #commentary is not removed.
 verbatim::
 	Do not change the message at all.
+scissors::
+	Same as `whitespace`, except that everything from (and
+	including) the line
+	"`# ------------------------ >8 ------------------------`"
+	is truncated if the message is to be edited. "`#`" can be
+	customized with core.commentChar.
 default::
 	Same as `strip` if the message is to be edited.
 	Otherwise `whitespace`.

builtin/commit.c

@@ -113,6 +113,7 @@ static char *sign_commit;
 static enum {
 	CLEANUP_SPACE,
 	CLEANUP_NONE,
+	CLEANUP_SCISSORS,
 	CLEANUP_ALL
 } cleanup_mode;
 static const char *cleanup_arg;
@@ -754,7 +755,9 @@ static int prepare_to_commit(const char *index_file, const char *prefix,
 	strbuf_addstr(&committer_ident, git_committer_info(IDENT_STRICT));
 	if (use_editor && include_status) {
 		char *ai_tmp, *ci_tmp;
-		if (whence != FROM_COMMIT)
+		if (whence != FROM_COMMIT) {
+			if (cleanup_mode == CLEANUP_SCISSORS)
+				wt_status_add_cut_line(s->fp);
 			status_printf_ln(s, GIT_COLOR_NORMAL,
 			    whence == FROM_MERGE
 				? _("\n"
@@ -770,13 +773,16 @@ static int prepare_to_commit(const char *index_file, const char *prefix,
 				git_path(whence == FROM_MERGE
 					 ? "MERGE_HEAD"
 					 : "CHERRY_PICK_HEAD"));
+		}
 
 		fprintf(s->fp, "\n");
 		if (cleanup_mode == CLEANUP_ALL)
 			status_printf(s, GIT_COLOR_NORMAL,
 				_("Please enter the commit message for your changes."
 				  " Lines starting\nwith '%c' will be ignored, and an empty"
 				  " message aborts the commit.\n"), comment_line_char);
+		else if (cleanup_mode == CLEANUP_SCISSORS && whence == FROM_COMMIT)
+			wt_status_add_cut_line(s->fp);
 		else /* CLEANUP_SPACE, that is. */
 			status_printf(s, GIT_COLOR_NORMAL,
 				_("Please enter the commit message for your changes."
@@ -1132,6 +1138,8 @@ static int parse_and_validate_options(int argc, const char *argv[],
 		cleanup_mode = CLEANUP_SPACE;
 	else if (!strcmp(cleanup_arg, "strip"))
 		cleanup_mode = CLEANUP_ALL;
+	else if (!strcmp(cleanup_arg, "scissors"))
+		cleanup_mode = use_editor ? CLEANUP_SCISSORS : CLEANUP_SPACE;
 	else
 		die(_("Invalid cleanup mode %s"), cleanup_arg);
 
@@ -1600,8 +1608,8 @@ int cmd_commit(int argc, const char **argv, const char *prefix)
 		die(_("could not read commit message: %s"), strerror(saved_errno));
 	}
 
-	/* Truncate the message just before the diff, if any. */
-	if (verbose)
+	if (verbose || /* Truncate the message just before the diff, if any. */
+	    cleanup_mode == CLEANUP_SCISSORS)
 		wt_status_truncate_message_at_cut_line(&sb);
 
 	if (cleanup_mode != CLEANUP_NONE)

t/t7502-commit.sh

@@ -223,6 +223,22 @@ test_expect_success 'cleanup commit messages (whitespace option,-F)' '
 
 '
 
+test_expect_success 'cleanup commit messages (scissors option,-F,-e)' '
+
+	echo >>negative &&
+	cat >text <<EOF &&
+
+# to be kept
+# ------------------------ >8 ------------------------
+to be removed
+EOF
+	echo "# to be kept" >expect &&
+	git commit --cleanup=scissors -e -F text -a &&
+	git cat-file -p HEAD |sed -e "1,/^\$/d">actual &&
+	test_cmp expect actual
+
+'
+
 test_expect_success 'cleanup commit messages (strip option,-F)' '
 
 	echo >>negative &&