dgit: unrepres. changes: Prepare to tolerate symlinks

Permit symlinks (which have mode 120000 in git) to make their way
through for more detailed checks.

No functional change except to error messages, because:

 * If neither thing was a symlink, then the existing regexps
   still match and the new "modified symlink" clause will not,
   so the flow is unchanged.

 * Otherwise, if both $oldmode and $newmode match [^0], ie,
   this is a modification rather than deletion or removal,
   we insist that $oldmode=$newmode, and then, fail the
   new "modified symlink" check.

 * Otherwise, we fail the check for default mode.

So in the case we are allowing to proceed further, we fail as before.

Signed-off-by: Ian Jackson <ijackson@chiark.greenend.org.uk>

2 files changed, 9 insertions, 8 deletions

diff --git a/dgit b/dgit
index dd3b31c..8b9934b 100755
--- a/dgit
+++ b/dgit
@@ -4910,14 +4910,15 @@ sub quiltify_trees_differ ($$;$$$) {
 
 	if ($unrepres) {
 	    eval {
-		die "not a plain file\n"
-		    unless $newmode =~ m/^10\d{4}$/ ||
-		           $oldmode =~ m/^10\d{4}$/;
+		die "not a plain file or symlink\n"
+		    unless $newmode =~ m/^(?:10|12)\d{4}$/ ||
+		           $oldmode =~ m/^(?:10|12)\d{4}$/;
 		if ($oldmode =~ m/[^0]/ &&
 		    $newmode =~ m/[^0]/) {
-		    die "mode changed\n" if $oldmode ne $newmode;
+		    die "mode or type changed\n" if $oldmode ne $newmode;
+		    die "modified symlink\n" unless $newmode =~ m/^10/;
 		} else {
-		    die "non-default mode\n"
+		    die "non-default mode or type\n"
 			unless $newmode =~ m/^100644$/ ||
 			       $oldmode =~ m/^100644$/;
 		}
diff --git a/tests/tests/unrepresentable b/tests/tests/unrepresentable
index fa71bd3..206af86 100755
--- a/tests/tests/unrepresentable
+++ b/tests/tests/unrepresentable
@@ -25,12 +25,12 @@ badly-2 () {
 	attempt
 }
 
-badly-1 orig-symlink 'not a plain file'
+badly-1 orig-symlink 'modified symlink'
 	ln -sf NEWTARGET orig-symlink
 	git add orig-symlink
 badly-2
 
-badly-1 orig-symlink 'not a plain file'
+badly-1 orig-symlink 'non-default mode or type'
 	git rm -f orig-symlink
 badly-2
 
@@ -39,7 +39,7 @@ start
 	git commit -m deleted
 attempt
 
-badly-1 src.c 'mode changed'
+badly-1 src.c 'mode or type changed'
 	chmod +x src.c
 	git add src.c
 badly-2