git-gui: Allow committing empty merges

Johannes Sixt noticed that git-gui would not let the user commit
a merge created by `git merge -s ours` as the ours strategy does
not alter the tree (that is HEAD^1^{tree} = HEAD^{tree} after the
merge).  The same issue arises from amending such a merge commit.

We now permit an empty commit (no changed files) if we are doing
a merge commit.  Core Git does this with its command line based
git-commit tool, so it makes sense for the GUI to do the same.

Signed-off-by: Shawn O. Pearce <spearce@spearce.org>

diff --git a/git-gui.sh b/git-gui.sh
index 1981827a8e8bcc2b2e43598bb06e3e6c87bd4d1d..0e448007f7c3cd4a109dd5920bc9d1fc6a21b483 100755 (executable)
--- a/git-gui.sh
+++ b/git-gui.sh
@@ -1171,7 +1171,7 @@ File [short_path $path] cannot be committed by this program.
                }
                }
        }
-       if {!$files_ready} {
+       if {!$files_ready && ![string match *merge $curType]} {
                info_popup {No changes to commit.
 
 You must add at least 1 file before you can commit.