X-Git-Url: http://www.chiark.greenend.org.uk/ucgi/~ianmdlvl/git?p=dgit.git;a=blobdiff_plain;f=git-debrebase;h=4bfe0952518214203c5e3ac397b27c53ceb93354;hp=f09508e1be90c859c60aa8a0220b1891853e86aa;hb=d82657683a77446101a644dec66fd0b83d18bf95;hpb=6a3fc22a4ad2b36bd799b1f9e3b7d65dcd4a6839

diff --git a/git-debrebase b/git-debrebase
index f09508e1..4bfe0952 100755
--- a/git-debrebase
+++ b/git-debrebase
@@ -433,11 +433,54 @@ sub ffq_prev_branchinfo () {
     return gdr_ffq_prev_branchinfo($current);
 }
 
-sub record_gdrlast ($$) {
-    my ($gdrlast, $newvalue) = @_;
-    push @deferred_updates, "update $gdrlast $newvalue $git_null_obj";
+sub record_gdrlast ($$;$) {
+    my ($gdrlast, $newvalue, $oldvalue) = @_;
+    $oldvalue ||= $git_null_obj;
+    push @deferred_updates, "update $gdrlast $newvalue $oldvalue";
 }
 
+sub fail_unprocessable ($) {
+    my ($msg) = @_;
+    changedir $maindir;
+    my ($ffqs, $ffqm, $symref, $ffq_prev, $gdrlast) = ffq_prev_branchinfo();
+
+    my $mangled = <<END;
+Branch/history seems mangled - no longer in gdr format.
+See ILLEGAL OPERATIONS in git-debrebase(5).
+END
+    chomp $mangled;
+
+    if (defined $ffqm) {
+	fail <<END;
+$msg
+Is this meant to be a gdr branch?  $ffqm
+END
+    } elsif (git_get_ref $ffq_prev) {
+	fail <<END;
+$msg
+$mangled
+Consider git-debrebase scrap, to throw away your recent work.
+END
+    } elsif (!git_get_ref $gdrlast) {
+	fail <<END;
+$msg
+Branch does not seem to be meant to be a git-debrebase branch?
+Wrong branch, or maybe you needed git-debrebase convert-from-*.
+END
+    } elsif (is_fast_fwd $gdrlast, git_rev_parse 'HEAD') {
+	fail <<END;
+$msg
+$mangled
+END
+    } else {
+	fail <<END;
+$msg
+Branch/history mangled, and diverged since last git-debrebase.
+Maybe you reset to, or rebased from, somewhere inappropriate.
+END
+    }
+};
+
 sub gbp_pq_export ($$$) {
     my ($bname, $base, $tip) = @_;
     # must be run in a workarea.  $bname and patch-queue/$bname
@@ -1053,7 +1096,7 @@ sub keycommits ($;$$$$$) {
     my $clogonly;
     my $cl;
     my $found_pm;
-    $fatal //= sub { fail $_[1]; };
+    $fatal //= sub { fail_unprocessable $_[1]; };
     my $x = sub {
 	my ($cb, $tagsfx, $mainwhy, $xwhy) = @_;
 	my $why = $mainwhy.$xwhy;
@@ -1178,7 +1221,7 @@ sub walk ($;$$$) {
 	if ($nogenerate) {
 	    return (undef,undef);
 	}
-	fail "found unprocessable commit, cannot cope".
+	fail_unprocessable "found unprocessable commit, cannot cope".
 	    (defined $cl->{Why} ? "; $cl->{Why}:": ':').
 	    " (commit $cur) (d.".
 	    (join ' ', map { sprintf "%#x", $_->{Differs} }
@@ -2411,12 +2454,23 @@ sub check_series_has_all_patches ($) {
 
 sub begin_convert_from () {
     my $head = get_head();
-    return ($head, undef);
+    my ($ffqs, $ffqm, $symref, $ffq_prev, $gdrlast) = ffq_prev_branchinfo();
+
+    fail "ffq-prev exists, this is already managed by git-debrebase!"
+	if $ffq_prev && git_get_ref $ffq_prev;
+
+    my $gdrlast_obj = $gdrlast && git_get_ref $gdrlast;
+    snag 'already-converted',
+	"ahead of debrebase-last, this is already managed by git-debrebase!"
+	if $gdrlast_obj && is_fast_fwd $gdrlast_obj, $head;
+    return ($head, { LastRef => $gdrlast, LastObj => $gdrlast_obj });
 }
 
 sub complete_convert_from ($$$$) {
     my ($old_head, $new_head, $gi, $mrest) = @_;
     ffq_check $new_head;
+    record_gdrlast $gi->{LastRef}, $new_head, $gi->{LastObj}
+	if $gi->{LastRef};
     snags_maybe_bail();
     update_head_checkout $old_head, $new_head, $mrest;
 }