git svn: handle errors and concurrent commits in dcommit

dcommit didn't handle errors returned by SVN and coped very
poorly with concurrent commits that appear in SVN repository
while dcommit was running. In both cases it left git repository
in inconsistent state: index (which was reset with `git reset
--mixed' after a successful commit to SVN) no longer matched the
checkouted tree, when the following commit failed or needed to be
rebased. See http://bugs.debian.org/676904 for examples.

This patch fixes the issues by:
- introducing error handler for dcommit. The handler will try
  to rebase or reset working tree before returning error to the
  end user. dcommit_rebase function was extracted out of cmd_dcommit
  to ensure consistency between cmd_dcommit and the error handler.
- calling `git reset --mixed' only once after all patches are
  successfully committed to SVN. This ensures index is not touched
  for most of the time of dcommit run.

Signed-off-by: Eric Wong <normalperson@yhbt.net>

1 files changed, 55 insertions, 19 deletions

diff --git a/git-svn.perl b/git-svn.perl
index 5711c5719..828b8f0c8 100755
--- a/git-svn.perl
+++ b/git-svn.perl
@@ -777,6 +777,44 @@ sub populate_merge_info {
 	return undef;
 }
 
+sub dcommit_rebase {
+	my ($is_last, $current, $fetched_ref, $svn_error) = @_;
+	my @diff;
+
+	if ($svn_error) {
+		print STDERR "\nERROR from SVN:\n",
+				$svn_error->expanded_message, "\n";
+	}
+	unless ($_no_rebase) {
+		# we always want to rebase against the current HEAD,
+		# not any head that was passed to us
+		@diff = command('diff-tree', $current,
+	                   $fetched_ref, '--');
+		my @finish;
+		if (@diff) {
+			@finish = rebase_cmd();
+			print STDERR "W: $current and ", $fetched_ref,
+			             " differ, using @finish:\n",
+			             join("\n", @diff), "\n";
+		} elsif ($is_last) {
+			print "No changes between ", $current, " and ",
+			      $fetched_ref,
+			      "\nResetting to the latest ",
+			      $fetched_ref, "\n";
+			@finish = qw/reset --mixed/;
+		}
+		command_noisy(@finish, $fetched_ref) if @finish;
+	}
+	if ($svn_error) {
+		die "ERROR: Not all changes have been committed into SVN"
+			.($_no_rebase ? ".\n" : ", however the committed\n"
+			."ones (if any) seem to be successfully integrated "
+			."into the working tree.\n")
+			."Please see the above messages for details.\n";
+	}
+	return @diff;
+}
+
 sub cmd_dcommit {
 	my $head = shift;
 	command_noisy(qw/update-index --refresh/);
@@ -904,6 +942,7 @@ sub cmd_dcommit {
 	}
 
 	my $rewritten_parent;
+	my $current_head = command_oneline(qw/rev-parse HEAD/);
 	Git::SVN::remove_username($expect_url);
 	if (defined($_merge_info)) {
 		$_merge_info =~ tr{ }{\n};
@@ -943,6 +982,14 @@ sub cmd_dcommit {
 			                },
 					mergeinfo => $_merge_info,
 			                svn_path => '');
+
+			my $err_handler = $SVN::Error::handler;
+			$SVN::Error::handler = sub {
+				my $err = shift;
+				dcommit_rebase(1, $current_head, $gs->refname,
+					$err);
+			};
+
 			if (!Git::SVN::Editor->new(\%ed_opts)->apply_diff) {
 				print "No changes\n$d~1 == $d\n";
 			} elsif ($parents->{$d} && @{$parents->{$d}}) {
@@ -950,31 +997,19 @@ sub cmd_dcommit {
 				                               $parents->{$d};
 			}
 			$_fetch_all ? $gs->fetch_all : $gs->fetch;
+			$SVN::Error::handler = $err_handler;
 			$last_rev = $cmt_rev;
 			next if $_no_rebase;
 
-			# we always want to rebase against the current HEAD,
-			# not any head that was passed to us
-			my @diff = command('diff-tree', $d,
-			                   $gs->refname, '--');
-			my @finish;
-			if (@diff) {
-				@finish = rebase_cmd();
-				print STDERR "W: $d and ", $gs->refname,
-				             " differ, using @finish:\n",
-				             join("\n", @diff), "\n";
-			} else {
-				print "No changes between current HEAD and ",
-				      $gs->refname,
-				      "\nResetting to the latest ",
-				      $gs->refname, "\n";
-				@finish = qw/reset --mixed/;
-			}
-			command_noisy(@finish, $gs->refname);
+			my @diff = dcommit_rebase(@$linear_refs == 0, $d,
+						$gs->refname, undef);
 
-			$rewritten_parent = command_oneline(qw/rev-parse HEAD/);
+			$rewritten_parent = command_oneline(qw/rev-parse/,
+							$gs->refname);
 
 			if (@diff) {
+				$current_head = command_oneline(qw/rev-parse
+								HEAD/);
 				@refs = ();
 				my ($url_, $rev_, $uuid_, $gs_) =
 				              working_head_info('HEAD', \@refs);
@@ -1019,6 +1054,7 @@ sub cmd_dcommit {
 				}
 				$parents = \%p;
 				$linear_refs = \@l;
+				undef $last_rev;
 			}
 		}
 	}