[PATCH 1/2] git-commit: Disallow unchanged tree in non-merge mode

["Dmitry V. Levin" <ldv@altlinux.org>]

Do not commit an unchanged tree in non-merge mode.

While regular mode is already handled by git-runstatus, this cheap check
allows to avoid costly git-runstatus later.  Also, amend mode needs
special attention, because git-runstatus return value is ignored.
The idea is that amend should not commit an unchanged tree,
one should just remove the top commit using git-reset instead.

Signed-off-by: Dmitry V. Levin <ldv@altlinux.org>
---
 git-commit.sh |   10 ++++++++++
 1 files changed, 10 insertions(+), 0 deletions(-)

diff --git a/git-commit.sh b/git-commit.sh
index 1d04f1f..800f96c 100755
--- a/git-commit.sh
+++ b/git-commit.sh
@@ -629,6 +629,16 @@ then
 		tree=$(GIT_INDEX_FILE="$TMP_INDEX" git write-tree) &&
 		rm -f "$TMP_INDEX"
 	fi &&
+	if test -n "$current" -a ! -f "$GIT_DIR/MERGE_HEAD"
+	then
+		current_tree="$(git cat-file commit "$current${amend:+^}" 2>/dev/null |
+				sed -e '/^tree \+/!d' -e 's///' -e q)"
+		if test "$tree" = "$current_tree"
+		then
+			echo >&2 "nothing to commit${amend:+ (use \"git reset HEAD^\" to remove the top commit)}"
+			false
+		fi
+	fi &&
 	commit=$(git commit-tree $tree $PARENTS <"$GIT_DIR/COMMIT_MSG") &&
 	rlogm=$(sed -e 1q "$GIT_DIR"/COMMIT_MSG) &&
 	git update-ref -m "$GIT_REFLOG_ACTION: $rlogm" HEAD $commit "$current" &&
-- 
ldv