X-Git-Url: https://sipb.mit.edu/gitweb.cgi/ikiwiki.git/blobdiff_plain/4fcf25a8200a25a850f095ac90b5ac9f4e395664..c2c943bc25a83b5c4c3eab3b43a7b6e4c4f4ba33:/IkiWiki/Rcs/monotone.pm?ds=inline

diff --git a/IkiWiki/Rcs/monotone.pm b/IkiWiki/Rcs/monotone.pm
index 0435dc45c..992065931 100644
--- a/IkiWiki/Rcs/monotone.pm
+++ b/IkiWiki/Rcs/monotone.pm
@@ -10,7 +10,7 @@ package IkiWiki;
 
 my $sha1_pattern = qr/[0-9a-fA-F]{40}/; # pattern to validate sha1sums
 
-sub check_config() {
+sub check_config() { #{{{
 	if (!defined($config{mtnrootdir})) {
 		$config{mtnrootdir} = $config{srcdir};
 	}
@@ -24,20 +24,20 @@ sub check_config() {
 	
 	chdir $config{srcdir}
 	    or error("Cannot chdir to $config{srcdir}: $!");
-}
+} #}}}
 
-sub get_rev () {
+sub get_rev () { #{{{
 	my $sha1 = `mtn --root=$config{mtnrootdir} automate get_base_revision_id`;
 
 	($sha1) = $sha1 =~ m/($sha1_pattern)/; # sha1 is untainted now
 	if (! $sha1) {
-		warn("Unable to get base revision for '$config{srcdir}'.")
+		debug("Unable to get base revision for '$config{srcdir}'.")
 	}
 
 	return $sha1;
-}
+} #}}}
 
-sub get_rev_auto ($) {
+sub get_rev_auto ($) { #{{{
 	my $automator=shift;
 
 	my @results = $automator->call("get_base_revision_id");
@@ -45,27 +45,29 @@ sub get_rev_auto ($) {
 	my $sha1 = $results[0];
 	($sha1) = $sha1 =~ m/($sha1_pattern)/; # sha1 is untainted now
 	if (! $sha1) {
-		warn("Unable to get base revision for '$config{srcdir}'.")
+		debug("Unable to get base revision for '$config{srcdir}'.")
 	}
 
 	return $sha1;
-}
-
-sub mtn_merge ($$$$$) {
-    my $leftRev=shift;
-    my $rightRev=shift;
-    my $branch=shift;
-    my $author=shift;
-    my $message=shift;	# ignored for the moment because mtn doesn't support it
+} #}}}
+
+sub mtn_merge ($$$$) { #{{{
+	my $leftRev=shift;
+	my $rightRev=shift;
+	my $branch=shift;
+	my $author=shift;
     
-    my $mergeRev;
+	my $mergeRev;
 
 	my $mergerc = $config{mtnmergerc};
     
 	my $child = open(MTNMERGE, "-|");
 	if (! $child) {
 		open STDERR, ">&STDOUT";
-		exec("mtn", "--root=$config{mtnrootdir}", "--rcfile", $mergerc, "explicit_merge", $leftRev, $rightRev, $branch, "--author", $author, "--key", $config{mtnkey}) || error("mtn merge failed to run");
+		exec("mtn", "--root=$config{mtnrootdir}", "--rcfile",
+		     $mergerc, "explicit_merge", $leftRev, $rightRev,
+		     $branch, "--author", $author, "--key", 
+		     $config{mtnkey}) || error("mtn merge failed to run");
 	}
 
 	while (<MTNMERGE>) {
@@ -76,12 +78,12 @@ sub mtn_merge ($$$$$) {
 	
 	close MTNMERGE || return undef;
 
-	warn("merged $leftRev, $rightRev to make $mergeRev");
+	debug("merged $leftRev, $rightRev to make $mergeRev");
 
 	return $mergeRev;
-}
+} #}}}
 
-sub commit_file_to_new_rev($$$$$$$$) {
+sub commit_file_to_new_rev($$$$$$$$) { #{{{
 	my $automator=shift;
 	my $wsfilename=shift;
 	my $oldFileID=shift;
@@ -94,98 +96,51 @@ sub commit_file_to_new_rev($$$$$$$$) {
 	#store the file
 	my ($out, $err) = $automator->call("put_file", $oldFileID, $newFileContents);
 	my ($newFileID) = ($out =~ m/^($sha1_pattern)$/);
-	error("Failed to store file data for $wsfilename in repository") if (!defined($newFileID) || 40 != length $newFileID);
+	error("Failed to store file data for $wsfilename in repository")
+		if (! defined $newFileID || length $newFileID != 40);
 
 	# get the mtn filename rather than the workspace filename
 	($out, $err) = $automator->call("get_corresponding_path", $oldrev, $wsfilename, $oldrev);
 	my ($filename) = ($out =~ m/^file "(.*)"$/);
 	error("Couldn't find monotone repository path for file $wsfilename") if (! $filename);
-	warn("Converted ws filename of $wsfilename to repos filename of $filename");
+	debug("Converted ws filename of $wsfilename to repos filename of $filename");
 
 	# then stick in a new revision for this file
-	my $manifest =  "format_version \"1\"\n\n".
-					"new_manifest [0000000000000000000000000000000000000000]\n\n".
-					"old_revision [$oldrev]\n\n".
-					"patch \"$filename\"\n".
-					" from [$oldFileID]\n".
-					"   to [$newFileID]\n";
+	my $manifest = "format_version \"1\"\n\n".
+	               "new_manifest [0000000000000000000000000000000000000000]\n\n".
+	               "old_revision [$oldrev]\n\n".
+	               "patch \"$filename\"\n".
+	               " from [$oldFileID]\n".
+	               "   to [$newFileID]\n";
 	($out, $err) = $automator->call("put_revision", $manifest);
 	my ($newRevID) = ($out =~ m/^($sha1_pattern)$/);
-	error("Unable to make new monotone repository revision") if (!defined($newRevID) || 40 != length $newRevID);
-	warn("put revision: $newRevID");
+	error("Unable to make new monotone repository revision")
+		if (! defined $newRevID || length $newRevID != 40);
+	debug("put revision: $newRevID");
 	
 	# now we need to add certs for this revision...
 	# author, branch, changelog, date
 	$automator->call("cert", $newRevID, "author", $author);
 	$automator->call("cert", $newRevID, "branch", $branch);
 	$automator->call("cert", $newRevID, "changelog", $message);
-	$automator->call("cert", $newRevID, "date", time2str("%Y-%m-%dT%T", time, "UTC"));
+	$automator->call("cert", $newRevID, "date",
+		time2str("%Y-%m-%dT%T", time, "UTC"));
 	
-	warn("Added certs for rev: $newRevID");
+	debug("Added certs for rev: $newRevID");
 	return $newRevID;
-}
+} #}}}
 
-sub check_mergerc() {
+sub check_mergerc () { #{{{
 	my $mergerc = $config{mtnmergerc};
 	if (! -r $mergerc ) {
-		warn("$mergerc doesn't exist.  Creating file with default mergers.");
-		open(DATA, ">$mergerc") or error("can't open $mergerc $!");
-		my $defaultrc = "".
-"	function local_execute_redirected(stdin, stdout, stderr, path, ...)\n".
-"	   local pid\n".
-"	   local ret = -1\n".
-"	   io.flush();\n".
-"	   pid = spawn_redirected(stdin, stdout, stderr, path, unpack(arg))\n".
-"	   if (pid ~= -1) then ret, pid = wait(pid) end\n".
-"	   return ret\n".
-"	end\n".
-"	if (not execute_redirected) then -- use standard function if available\n".
-"	   execute_redirected = local_execute_redirected\n".
-"	end\n".
-"	if (not mergers.fail) then -- use standard merger if available\n".
-"	   mergers.fail = {\n".
-"	      cmd = function (tbl) return false end,\n".
-"	      available = function () return true end,\n".
-"	      wanted = function () return true end\n".
-"	   }\n".
-"	end\n".
-"	mergers.diffutils_force = {\n".
-"	   cmd = function (tbl)\n".
-"	      local ret = execute_redirected(\n".
-"	          \"\",\n".
-"	          tbl.outfile,\n".
-"	          \"\",\n".
-"	          \"diff3\",\n".
-"	          \"--merge\",\n".
-"	          \"--show-overlap\",\n".
-"	          \"--label\", string.format(\"[Yours]\",     tbl.left_path ),\n".
-"	          \"--label\", string.format(\"[Original]\",  tbl.anc_path  ),\n".
-"	          \"--label\", string.format(\"[Theirs]\",    tbl.right_path),\n".
-"	          tbl.lfile,\n".
-"	          tbl.afile,\n".
-"	          tbl.rfile\n".
-"	      )\n".
-"	      if (ret > 1) then\n".
-"	         io.write(gettext(\"Error running GNU diffutils 3-way difference tool 'diff3'\"))\n".
-"	         return false\n".
-"	      end\n".
-"	      return tbl.outfile\n".
-"	   end,\n".
-"	   available =\n".
-"	      function ()\n".
-"	          return program_exists_in_path(\"diff3\");\n".
-"	      end,\n".
-"	   wanted =\n".
-"	      function ()\n".
-"	           return true\n".
-"	      end\n".
-"	}\n";
-		print DATA $defaultrc;
-		close(DATA);
+		debug("$mergerc doesn't exist. Creating file with default mergers.");
+		open (my $out, ">", $mergerc) or error("can't open $mergerc: $!");
+		print $out <DATA>;
+		close $out;
 	}
-}
+} #}}}
 
-sub read_certs ($$) {
+sub read_certs ($$) { #{{{
 	my $automator=shift;
 	my $rev=shift;
 	my @results = $automator->call("certs", $rev);
@@ -203,9 +158,9 @@ sub read_certs ($$) {
 	}
 
 	return @ret;
-}
+} #}}}
 
-sub get_changed_files ($$) {
+sub get_changed_files ($$) { #{{{
 	my $automator=shift;
 	my $rev=shift;
 	
@@ -217,38 +172,33 @@ sub get_changed_files ($$) {
 	
 	while ($changes =~ m/\s*(add_file|patch|delete|rename)\s"(.*?)(?<!\\)"\n/sg) {
 		my $file = $2;
-		if (! $seen{$file}) {	# don't add the same file multiple times
+		# don't add the same file multiple times
+		if (! $seen{$file}) {
 			push @ret, $file;
 			$seen{$file} = 1;
 		}
 	}
 	
 	return @ret;
-}
-
-# The following functions are the ones actually called by Ikiwiki
-
-sub rcs_update () {
-	# Update working directory to current version.
+} #}}}
 
+sub rcs_update () { #{{{
 	check_config();
 
 	if (defined($config{mtnsync}) && $config{mtnsync}) {
-		if (system("mtn", "--root=$config{mtnrootdir}", "sync", "--quiet", "--ticker=none", "--key", $config{mtnkey}) != 0) {
-			warn("monotone sync failed before update\n");
+		if (system("mtn", "--root=$config{mtnrootdir}", "sync",
+		           "--quiet", "--ticker=none", 
+		           "--key", $config{mtnkey}) != 0) {
+			debug("monotone sync failed before update");
 		}
 	}
 
 	if (system("mtn", "--root=$config{mtnrootdir}", "update", "--quiet") != 0) {
-		warn("monotone update failed\n");
+		debug("monotone update failed");
 	}
-}
+} #}}}
 
-sub rcs_prepedit ($) {
-	# Prepares to edit a file under revision control. Returns a token
-	# that must be passed into rcs_commit when the file is ready
-	# for committing.
-	# The file is relative to the srcdir.
+sub rcs_prepedit ($) { #{{{
 	my $file=shift;
 
 	check_config();
@@ -256,9 +206,9 @@ sub rcs_prepedit ($) {
 	# For monotone, return the revision of the file when
 	# editing begins.
 	return get_rev();
-}
+} #}}}
 
-sub rcs_commit ($$$;$$) {
+sub rcs_commit ($$$;$$) { #{{{
 	# Tries to commit the page; returns undef on _success_ and
 	# a version of the page with the rcs's conflict markers on failure.
 	# The file is relative to the srcdir.
@@ -295,14 +245,17 @@ sub rcs_commit ($$$;$$) {
 		# FIXME: use of $file in these backticks is not wise from a
 		# security POV. Probably safe, but should be avoided
 		# anyway.
+		# At the moment the backticks are used because the above call using the automate
+		# interface was failing.  When that bug in monotone is fixed, we should switch
+		# back.
 		my $diff = `mtn --root=$config{mtnrootdir} au content_diff -r $oldrev -r $rev $file`; # was just $out;
 
 		if ($diff) {
-			# this file has changed
-			# commit a revision with just this file changed off
-			# the old revision
+			# Commit a revision with just this file changed off
+			# the old revision.
+			#
 			# first get the contents
-			warn("File changed: forming branch\n");
+			debug("File changed: forming branch");
 			my $newfile=readfile("$config{srcdir}/$file");
 			
 			# then get the old content ID from the diff
@@ -324,52 +277,55 @@ sub rcs_commit ($$$;$$) {
 
 			# if we made it to here then the file has been committed... revert the local copy
 			if (system("mtn", "--root=$config{mtnrootdir}", "revert", $file) != 0) {
-				warn("Unable to revert $file after merge on conflicted commit!");
+				debug("Unable to revert $file after merge on conflicted commit!");
 			}
-			warn("Divergence created!  Attempting auto-merge.");
+			debug("Divergence created! Attempting auto-merge.");
 
 			check_mergerc();
 
 			# see if it will merge cleanly
 			$ENV{MTN_MERGE}="fail";
-			my $mergeResult = mtn_merge($newRevID, $rev, $branch, $author, "Auto-merging parallel web edits.");
+			my $mergeResult = mtn_merge($newRevID, $rev, $branch, $author);
 			$ENV{MTN_MERGE}="";
 
 			# push any changes so far
 			if (defined($config{mtnsync}) && $config{mtnsync}) {
 				if (system("mtn", "--root=$config{mtnrootdir}", "push", "--quiet", "--ticker=none", "--key", $config{mtnkey}) != 0) {
-					warn("monotone push failed\n");
+					debug("monotone push failed");
 				}
 			}
 			
 			if (defined($mergeResult)) {
 				# everything is merged - bring outselves up to date
-				if (system("mtn", "--root=$config{mtnrootdir}", "update", "-r", $mergeResult) != 0) {
-					warn("Unable to update to rev $mergeResult after merge on conflicted commit!");
+				if (system("mtn", "--root=$config{mtnrootdir}",
+				           "update", "-r", $mergeResult) != 0) {
+					debug("Unable to update to rev $mergeResult after merge on conflicted commit!");
 				}
-			} else {
-				warn("Auto-merge failed.  Using diff-merge to add conflict markers.");
+			}
+			else {
+				debug("Auto-merge failed.  Using diff-merge to add conflict markers.");
 				
 				$ENV{MTN_MERGE}="diffutils_force";
-				my $mergeResult = mtn_merge($newRevID, $rev, $branch, $author, "Merge parallel conflicting web edits (adding inline conflict markers).\nThis revision should be cleaned up manually.");
+				$mergeResult = mtn_merge($newRevID, $rev, $branch, $author);
 				$ENV{MTN_MERGE}="";
 				
 				if (!defined($mergeResult)) {
-					warn("Unable to insert conflict markers!");
-					error("Your commit succeeded.  Unfortunately, someone else committed something to the same\n".
-				 		"part of the wiki at the same time.  Both versions are stored in the monotone repository,\n".
-						"but at present the different versions cannot be reconciled through the web interface.\n\n".
-						"Please use the non-web interface to resolve the conflicts.\n");
+					debug("Unable to insert conflict markers!");
+					error("Your commit succeeded. Unfortunately, someone else committed something to the same ".
+				 		"part of the wiki at the same time. Both versions are stored in the monotone repository, ".
+						"but at present the different versions cannot be reconciled through the web interface. ".
+						"Please use the non-web interface to resolve the conflicts.");
 				}
 				
-				# suspend this revision because it has conflict markers...
-				if (system("mtn", "--root=$config{mtnrootdir}", "update", "-r", $mergeResult) != 0) {
-					warn("Unable to update to rev $mergeResult after conflict-enhanced merge on conflicted commit!");
+				if (system("mtn", "--root=$config{mtnrootdir}",
+				           "update", "-r", $mergeResult) != 0) {
+					debug("Unable to update to rev $mergeResult after conflict-enhanced merge on conflicted commit!");
 				}
 				
-				# return "conflict enhanced" file to the user for cleanup
-				# note, this relies on the fact that ikiwiki seems to call rcs_prepedit() again
-				# after we return
+				# return "conflict enhanced" file to the user
+				# for cleanup note, this relies on the fact
+				# that ikiwiki seems to call rcs_prepedit()
+				# again after we return
 				return readfile("$config{srcdir}/$file");
 			}
 			return undef;
@@ -377,59 +333,43 @@ sub rcs_commit ($$$;$$) {
 		$automator->close();
 	}
 
-	# if we reached here then the file we're looking at hasn't changed since $oldrev.  Commit it.
+	# If we reached here then the file we're looking at hasn't changed
+	# since $oldrev. Commit it.
 
-	if (system("mtn", "--root=$config{mtnrootdir}", "commit", "--quiet", "--author", $author, "--key", $config{mtnkey},
-				"-m", possibly_foolish_untaint($message), $file) != 0) {
-		warn("Traditional commit failed!\nReturning data as conflict.\n");
+	if (system("mtn", "--root=$config{mtnrootdir}", "commit", "--quiet",
+	           "--author", $author, "--key", $config{mtnkey}, "-m",
+		   possibly_foolish_untaint($message), $file) != 0) {
+		debug("Traditional commit failed! Returning data as conflict.");
 		my $conflict=readfile("$config{srcdir}/$file");
-		if (system("mtn", "--root=$config{mtnrootdir}", "revert", "--quiet", $file) != 0) {
-			warn("monotone revert failed\n");
+		if (system("mtn", "--root=$config{mtnrootdir}", "revert",
+		           "--quiet", $file) != 0) {
+			debug("monotone revert failed");
 		}
 		return $conflict;
 	}
 	if (defined($config{mtnsync}) && $config{mtnsync}) {
-		if (system("mtn", "--root=$config{mtnrootdir}", "sync", "--quiet", "--ticker=none", "--key", $config{mtnkey}) != 0) {
-			warn("monotone sync failed\n");
+		if (system("mtn", "--root=$config{mtnrootdir}", "sync",
+		           "--quiet", "--ticker=none", "--key",
+		           $config{mtnkey}) != 0) {
+			debug("monotone sync failed");
 		}
 	}
 
 	return undef # success
-}
+} #}}}
 
-sub rcs_add ($) {
-	# Add a file. The filename is relative to the root of the srcdir.
+sub rcs_add ($) { #{{{
 	my $file=shift;
 
 	check_config();
 
-	if (system("mtn", "--root=$config{mtnrootdir}", "add", "--quiet", "$config{srcdir}/$file") != 0) {
+	if (system("mtn", "--root=$config{mtnrootdir}", "add", "--quiet",
+	           $file) != 0) {
 		error("Monotone add failed");
 	}
-}
-
-sub rcs_recentchanges ($) {
-	# Examine the RCS history and generate a list of recent changes.
-	# The data structure returned for each change is:
-	# {
-	# 	user => # name of user who made the change,
-	# 	committype => # either "web" or the name of the rcs,
-	# 	when => # time when the change was made,
-	# 	message => [
-	# 		{ line => "commit message line" },
-	# 		{ line => "commit message line" },
-	# 		# etc,
-	# 	],
-	# 	pages => [
-	# 		{
-	# 			page => # name of page changed,
-	#			diffurl => # optional url to a diff showing 
-	#			           # the changes,
-	# 		},
-	# 		# repeat for each page changed in this commit,
-	# 	],
-	# }
+} #}}}
 
+sub rcs_recentchanges ($) { #{{{
 	my $num=shift;
 	my @ret;
 
@@ -443,18 +383,17 @@ sub rcs_recentchanges ($) {
 
 	my $child = open(MTNLOG, "-|");
 	if (! $child) {
-		exec("mtn", "log", "--root=$config{mtnrootdir}", "--no-graph", "--brief") || error("mtn log failed to run");
+		exec("mtn", "log", "--root=$config{mtnrootdir}", "--no-graph",
+		     "--brief") || error("mtn log failed to run");
 	}
 
-	my $line;
-
-	while (($num >= 0) and ($line = <MTNLOG>)) {
+	while (($num >= 0) and (my $line = <MTNLOG>)) {
 		if ($line =~ m/^($sha1_pattern)/) {
 			push @revs, $1;
 			$num -= 1;
 		}
 	}
-	close MTNLOG || warn "mtn log exited $?";
+	close MTNLOG || debug("mtn log exited $?");
 
 	my $automator = Monotone->new();
 	$automator->open(undef, $config{mtnrootdir});
@@ -471,10 +410,12 @@ sub rcs_recentchanges ($) {
 		my (@pages, @message);
 		
 		foreach my $cert (@$certs) {
-			if ($cert->{signature} eq "ok" && $cert->{trust} eq "trusted") {
+			if ($cert->{signature} eq "ok" &&
+			    $cert->{trust} eq "trusted") {
 				if ($cert->{name} eq "author") {
 					$user = $cert->{value};
-					# detect the source of the commit from the changelog
+				 	# detect the source of the commit
+					# from the changelog
 					if ($cert->{key} eq $config{mtnkey}) {
 						$committype = "web";
 					} else {
@@ -484,7 +425,8 @@ sub rcs_recentchanges ($) {
 					$when = time - str2time($cert->{value}, 'UTC');
 				} elsif ($cert->{name} eq "changelog") {
 					my $messageText = $cert->{value};
-					# split the changelog into multiple lines
+					# split the changelog into multiple
+					# lines
 					foreach my $msgline (split(/\n/, $messageText)) {
 						push @message, { line => $msgline };
 					}
@@ -514,15 +456,10 @@ sub rcs_recentchanges ($) {
 	$automator->close();
 
 	return @ret;
-}
+} #}}}
 
-sub rcs_notify () {
-	# This function is called when a change is committed to the wiki,
-	# and ikiwiki is running as a post-commit hook from the RCS.
-	# It should examine the repository to somehow determine what pages
-	# changed, and then send emails to users subscribed to those pages.
-	
-	warn("The monotone rcs_notify function is currently untested.  Use at own risk!");
+sub rcs_notify () { #{{{
+	debug("The monotone rcs_notify function is currently untested. Use at own risk!");
 	
 	if (! exists $ENV{REV}) {
 		error(gettext("REV is not set, not running from mtn post-commit hook, cannot send notifications"));
@@ -565,19 +502,19 @@ sub rcs_notify () {
 		},
 		sub {
 			`mtn --root=$config{mtnrootdir} au content_diff -r $rev`;
-		}, $user, @changed_pages);
-}
+		},
+		$user, @changed_pages);
+} #}}}
 
-sub rcs_getctime ($) {
-	# Optional, used to get the page creation time from the RCS.
-	# error gettext("getctime not implemented");
+sub rcs_getctime ($) { #{{{
 	my $file=shift;
 
 	check_config();
 
 	my $child = open(MTNLOG, "-|");
 	if (! $child) {
-		exec("mtn", "log", "--root=$config{mtnrootdir}", "--no-graph", "--brief", $file) || error("mtn log $file failed to run");
+		exec("mtn", "log", "--root=$config{mtnrootdir}", "--no-graph",
+		     "--brief", $file) || error("mtn log $file failed to run");
 	}
 
 	my $firstRev;
@@ -586,10 +523,10 @@ sub rcs_getctime ($) {
 			$firstRev=$1;
 		}
 	}
-	close MTNLOG || warn "mtn log $file exited $?";
+	close MTNLOG || debug("mtn log $file exited $?");
 
 	if (! defined $firstRev) {
-		warn "failed to parse mtn log for $file\n";
+		debug "failed to parse mtn log for $file";
 		return 0;
 	}
 
@@ -611,11 +548,66 @@ sub rcs_getctime ($) {
 	}
 
 	if (! defined $date) {
-		warn "failed to find date cert for revision $firstRev when looking for creation time of $file\n";
+		debug "failed to find date cert for revision $firstRev when looking for creation time of $file";
 		return 0;
 	}
 
 	$date=str2time($date, 'UTC');
 	debug("found ctime ".localtime($date)." for $file");
 	return $date;
-}
+} #}}}
+
+1
+
+# default mergerc content
+__DATA__
+	function local_execute_redirected(stdin, stdout, stderr, path, ...)
+	   local pid
+	   local ret = -1
+	   io.flush();
+	   pid = spawn_redirected(stdin, stdout, stderr, path, unpack(arg))
+	   if (pid ~= -1) then ret, pid = wait(pid) end
+	   return ret
+	end
+	if (not execute_redirected) then -- use standard function if available
+	   execute_redirected = local_execute_redirected
+	end
+	if (not mergers.fail) then -- use standard merger if available
+	   mergers.fail = {
+	      cmd = function (tbl) return false end,
+	      available = function () return true end,
+	      wanted = function () return true end
+	   }
+	end
+	mergers.diffutils_force = {
+	   cmd = function (tbl)
+	      local ret = execute_redirected(
+	          "",
+	          tbl.outfile,
+	          "",
+	          "diff3",
+	          "--merge",
+	          "--show-overlap",
+	          "--label", string.format("[Yours]",     tbl.left_path ),
+	          "--label", string.format("[Original]",  tbl.anc_path  ),
+	          "--label", string.format("[Theirs]",    tbl.right_path),
+	          tbl.lfile,
+	          tbl.afile,
+	          tbl.rfile
+	      )
+	      if (ret > 1) then
+	         io.write(gettext("Error running GNU diffutils 3-way difference tool 'diff3'"))
+	         return false
+	      end
+	      return tbl.outfile
+	   end,
+	   available =
+	      function ()
+	          return program_exists_in_path("diff3");
+	      end,
+	   wanted =
+	      function ()
+	           return true
+	      end
+	}
+EOF