dgit: When source discrepancy involves mode changes, report them specially.

Closes:#886442.

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

1 files changed, 29 insertions, 1 deletions

diff --git a/dgit b/dgit
index aa8f771..2e51f76 100755
--- a/dgit
+++ b/dgit
@@ -4240,7 +4240,35 @@ END
 	if ($r==256) {
 	    my $referent = $split_brain ? $dgithead : 'HEAD';
 	    my $diffs = cmdoutput @git, qw(diff --stat), $tree, $dgithead;
-	    fail <<END
+
+	    my @mode_changes;
+	    my $raw = cmdoutput @git,
+		qw(diff --no-renames -z -r --raw), $tree, $dgithead;
+	    my $changed;
+	    foreach (split /\0/, $raw) {
+		if (defined $changed) {
+		    push @mode_changes, "$changed: $_\n" if $changed;
+		    $changed = undef;
+		    next;
+		} elsif (m/^:0+ 0+ /) {
+		    $changed = '';
+		} elsif (m/^:(?:10*)?(\d+) (?:10*)?(\d+) /) {
+		    $changed = "Mode change from $1 to $2"
+		} else {
+		    die "$_ ?";
+		}
+	    }
+	    if (@mode_changes) {
+		fail <<END.(join '', @mode_changes).<<END;
+HEAD specifies a different tree to $dscfn:
+$diffs
+END
+There is a problem with your source tree (see dgit(7) for some hints).
+To see a full diff, run git diff $tree $referent
+END
+	    }
+
+	    fail <<END;
 HEAD specifies a different tree to $dscfn:
 $diffs
 Perhaps you forgot to build.  Or perhaps there is a problem with your