rebase -i: avoid 'git reset' when possible

When picking commits whose parents have not changed, we do not need to
rewrite the commit.  We do not need to reset the working directory to
the parent's state, either.

Requested by Sverre Rabbelier.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/git-rebase--interactive.sh b/git-rebase--interactive.sh
index 3dc659dd5896ce6c887eb786718919aef82f4ac6..314cd364b8f4df5e170dd0ffd9e874b3e6c2737c 100755 (executable)
--- a/git-rebase--interactive.sh
+++ b/git-rebase--interactive.sh
@@ -442,6 +442,30 @@ do_rest () {
        done
 }
 
+# skip picking commits whose parents are unchanged
+skip_unnecessary_picks () {
+       fd=3
+       while read command sha1 rest
+       do
+               # fd=3 means we skip the command
+               case "$fd,$command,$(git rev-parse --verify --quiet $sha1^)" in
+               3,pick,"$ONTO"*|3,p,"$ONTO"*)
+                       # pick a commit whose parent is current $ONTO -> skip
+                       ONTO=$sha1
+                       ;;
+               3,#*|3,,*)
+                       # copy comments
+                       ;;
+               *)
+                       fd=1
+                       ;;
+               esac
+               echo "$command${sha1:+ }$sha1${rest:+ }$rest" >&$fd
+       done <"$TODO" >"$TODO.new" 3>>"$DONE" &&
+       mv -f "$TODO".new "$TODO" ||
+       die "Could not skip unnecessary pick commands"
+}
+
 # check if no other options are set
 is_standalone () {
        test $# -eq 2 -a "$2" = '--' &&
@@ -746,6 +770,8 @@ EOF
                has_action "$TODO" ||
                        die_abort "Nothing to do"
 
+               test -d "$REWRITTEN" || skip_unnecessary_picks
+
                git update-ref ORIG_HEAD $HEAD
                output git checkout $ONTO && do_rest
                ;;

diff --git a/t/t3404-rebase-interactive.sh b/t/t3404-rebase-interactive.sh
index 603b003edff6d32fe8725f119778658c76c806fb..c32ff6682b932b3d9b270de7260a2671d8d07403 100755 (executable)
--- a/t/t3404-rebase-interactive.sh
+++ b/t/t3404-rebase-interactive.sh
@@ -459,4 +459,15 @@ test_expect_success 'submodule rebase -i' '
        FAKE_LINES="1 squash 2 3" git rebase -i A
 '
 
+test_expect_success 'avoid unnecessary reset' '
+       git checkout master &&
+       test-chmtime =123456789 file3 &&
+       git update-index --refresh &&
+       HEAD=$(git rev-parse HEAD) &&
+       git rebase -i HEAD~4 &&
+       test $HEAD = $(git rev-parse HEAD) &&
+       MTIME=$(test-chmtime -v +0 file3 | sed 's/[^0-9].*$//') &&
+       test 123456789 = $MTIME
+'
+
 test_done