Add a remote helper to interact with mediawiki (fetch & push)

Implement a gate between git and mediawiki, allowing git users to push
and pull objects from mediawiki just as one would do with a classic git
repository thanks to remote-helpers.

The following packages need to be installed (available on common
repositories):

  libmediawiki-api-perl
  libdatetime-format-iso8601-perl

Use remote helpers in order to be as transparent as possible to the git
user.

Download Mediawiki revisions through the Mediawiki API and then
fast-import into git.

Mediawiki revision number and git commits are linked thanks to notes
bound to commits.

The import part is done on a refs/mediawiki/<remote> branch before
coming to refs/remote/origin/master (Huge thanks to Jonathan Nieder
for his help)

We use UTF-8 everywhere: use encoding 'utf8'; does most of the job, but
we also read the output of Git commands in UTF-8 with the small helper
run_git, and write to the console (STDERR) in UTF-8. This allows a
seamless use of non-ascii characters in page titles, but hasn't been
tested on non-UTF-8 systems. In particular, UTF-8 encoding for filenames
could raise problems if different file systems handle UTF-8 filenames
differently. A uri_escape of mediawiki filenames could be imaginable, and
is still to be discussed further.

Partial cloning is supported using one of:

git clone -c remote.origin.pages='A_Page  Another_Page' mediawiki::http://wikiurl

git clone -c remote.origin.categories='Some_Category' mediawiki::http://wikiurl

git clone -c remote.origin.shallow='True' mediawiki::http://wikiurl

Thanks to notes metadata, it is possible to compare remote and local last
mediawiki revision to warn non-fast forward pushes and "everything
up-to-date" case.

When allowed, push looks for each commit between remotes/origin/master
and HEAD, catches every blob related to these commit and push them in
chronological order. To do so, it uses git rev-list --children HEAD and
travels the tree from remotes/origin/master to HEAD through children. In
other words:

* Shortest path from remotes/origin/master to HEAD
* For each commit encountered, push blobs related to this commit

Signed-off-by: Jérémie Nikaes <jeremie.nikaes@ensimag.imag.fr>
Signed-off-by: Arnaud Lacurie <arnaud.lacurie@ensimag.imag.fr>
Signed-off-by: Claire Fousse <claire.fousse@ensimag.imag.fr>
Signed-off-by: David Amouyal <david.amouyal@ensimag.imag.fr>
Signed-off-by: Matthieu Moy <matthieu.moy@grenoble-inp.fr>
Signed-off-by: Sylvain Boulmé <sylvain.boulme@imag.fr>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

2 files changed, 763 insertions, 0 deletions

diff --git a/contrib/mw-to-git/git-remote-mediawiki b/contrib/mw-to-git/git-remote-mediawiki
new file mode 100755
index 0000000000..d4d1198359
--- /dev/null
+++ b/contrib/mw-to-git/git-remote-mediawiki
@@ -0,0 +1,756 @@
+#! /usr/bin/perl
+
+# Copyright (C) 2011
+#     Jérémie Nikaes <jeremie.nikaes@ensimag.imag.fr>
+#     Arnaud Lacurie <arnaud.lacurie@ensimag.imag.fr>
+#     Claire Fousse <claire.fousse@ensimag.imag.fr>
+#     David Amouyal <david.amouyal@ensimag.imag.fr>
+#     Matthieu Moy <matthieu.moy@grenoble-inp.fr>
+# License: GPL v2 or later
+
+# Gateway between Git and MediaWiki.
+#   https://github.com/Bibzball/Git-Mediawiki/wiki
+#
+# Known limitations:
+#
+# - Only wiki pages are managed, no support for [[File:...]]
+#   attachments.
+#
+# - Poor performance in the best case: it takes forever to check
+#   whether we're up-to-date (on fetch or push) or to fetch a few
+#   revisions from a large wiki, because we use exclusively a
+#   page-based synchronization. We could switch to a wiki-wide
+#   synchronization when the synchronization involves few revisions
+#   but the wiki is large.
+#
+# - Git renames could be turned into MediaWiki renames (see TODO
+#   below)
+#
+# - login/password support requires the user to write the password
+#   cleartext in a file (see TODO below).
+#
+# - No way to import "one page, and all pages included in it"
+#
+# - Multiple remote MediaWikis have not been very well tested.
+
+use strict;
+use MediaWiki::API;
+use DateTime::Format::ISO8601;
+use encoding 'utf8';
+
+# use encoding 'utf8' doesn't change STDERROR
+# but we're going to output UTF-8 filenames to STDERR
+binmode STDERR, ":utf8";
+
+use URI::Escape;
+use warnings;
+
+# Mediawiki filenames can contain forward slashes. This variable decides by which pattern they should be replaced
+use constant SLASH_REPLACEMENT => "%2F";
+
+# It's not always possible to delete pages (may require some
+# priviledges). Deleted pages are replaced with this content.
+use constant DELETED_CONTENT => "[[Category:Deleted]]\n";
+
+# It's not possible to create empty pages. New empty files in Git are
+# sent with this content instead.
+use constant EMPTY_CONTENT => "<!-- empty page -->\n";
+
+# used to reflect file creation or deletion in diff.
+use constant NULL_SHA1 => "0000000000000000000000000000000000000000";
+
+my $remotename = $ARGV[0];
+my $url = $ARGV[1];
+
+# Accept both space-separated and multiple keys in config file.
+# Spaces should be written as _ anyway because we'll use chomp.
+my @tracked_pages = split(/[ \n]/, run_git("config --get-all remote.". $remotename .".pages"));
+chomp(@tracked_pages);
+
+# Just like @tracked_pages, but for MediaWiki categories.
+my @tracked_categories = split(/[ \n]/, run_git("config --get-all remote.". $remotename .".categories"));
+chomp(@tracked_categories);
+
+my $wiki_login = run_git("config --get remote.". $remotename .".mwLogin");
+# TODO: ideally, this should be able to read from keyboard, but we're
+# inside a remote helper, so our stdin is connect to git, not to a
+# terminal.
+my $wiki_passwd = run_git("config --get remote.". $remotename .".mwPassword");
+chomp($wiki_login);
+chomp($wiki_passwd);
+
+# Import only last revisions (both for clone and fetch)
+my $shallow_import = run_git("config --get --bool remote.". $remotename .".shallow");
+chomp($shallow_import);
+$shallow_import = ($shallow_import eq "true");
+
+my $wiki_name = $url;
+$wiki_name =~ s/[^\/]*:\/\///;
+
+# Commands parser
+my $entry;
+my @cmd;
+while (<STDIN>) {
+	chomp;
+	@cmd = split(/ /);
+	if (defined($cmd[0])) {
+		# Line not blank
+		if ($cmd[0] eq "capabilities") {
+			die("Too many arguments for capabilities") unless (!defined($cmd[1]));
+			mw_capabilities();
+		} elsif ($cmd[0] eq "list") {
+			die("Too many arguments for list") unless (!defined($cmd[2]));
+			mw_list($cmd[1]);
+		} elsif ($cmd[0] eq "import") {
+			die("Invalid arguments for import") unless ($cmd[1] ne "" && !defined($cmd[2]));
+			mw_import($cmd[1]);
+		} elsif ($cmd[0] eq "option") {
+			die("Too many arguments for option") unless ($cmd[1] ne "" && $cmd[2] ne "" && !defined($cmd[3]));
+			mw_option($cmd[1],$cmd[2]);
+		} elsif ($cmd[0] eq "push") {
+			mw_push($cmd[1]);
+		} else {
+			print STDERR "Unknown command. Aborting...\n";
+			last;
+		}
+	} else {
+		# blank line: we should terminate
+		last;
+	}
+
+	BEGIN { $| = 1 } # flush STDOUT, to make sure the previous
+			 # command is fully processed.
+}
+
+########################## Functions ##############################
+
+# MediaWiki API instance, created lazily.
+my $mediawiki;
+
+sub mw_connect_maybe {
+	if ($mediawiki) {
+	    return;
+	}
+	$mediawiki = MediaWiki::API->new;
+	$mediawiki->{config}->{api_url} = "$url/api.php";
+	if ($wiki_login) {
+		if (!$mediawiki->login({
+			lgname => $wiki_login,
+			lgpassword => $wiki_passwd,
+		})) {
+			print STDERR "Failed to log in mediawiki user \"$wiki_login\" on $url\n";
+			print STDERR "(error " .
+			    $mediawiki->{error}->{code} . ': ' .
+			    $mediawiki->{error}->{details} . ")\n";
+			exit 1;
+		} else {
+			print STDERR "Logged in with user \"$wiki_login\".\n";
+		}
+	}
+}
+
+sub get_mw_first_pages {
+	my $some_pages = shift;
+	my @some_pages = @{$some_pages};
+
+	my $pages = shift;
+
+	# pattern 'page1|page2|...' required by the API
+	my $titles = join('|', @some_pages);
+
+	my $mw_pages = $mediawiki->api({
+		action => 'query',
+		titles => $titles,
+	});
+	if (!defined($mw_pages)) {
+		print STDERR "fatal: could not query the list of wiki pages.\n";
+		print STDERR "fatal: '$url' does not appear to be a mediawiki\n";
+		print STDERR "fatal: make sure '$url/api.php' is a valid page.\n";
+		exit 1;
+	}
+	while (my ($id, $page) = each(%{$mw_pages->{query}->{pages}})) {
+		if ($id < 0) {
+			print STDERR "Warning: page $page->{title} not found on wiki\n";
+		} else {
+			$pages->{$page->{title}} = $page;
+		}
+	}
+}
+
+sub get_mw_pages {
+	mw_connect_maybe();
+
+	my %pages; # hash on page titles to avoid duplicates
+	my $user_defined;
+	if (@tracked_pages) {
+		$user_defined = 1;
+		# The user provided a list of pages titles, but we
+		# still need to query the API to get the page IDs.
+
+		my @some_pages = @tracked_pages;
+		while (@some_pages) {
+			my $last = 50;
+			if ($#some_pages < $last) {
+				$last = $#some_pages;
+			}
+			my @slice = @some_pages[0..$last];
+			get_mw_first_pages(\@slice, \%pages);
+			@some_pages = @some_pages[51..$#some_pages];
+		}
+	}
+	if (@tracked_categories) {
+		$user_defined = 1;
+		foreach my $category (@tracked_categories) {
+			if (index($category, ':') < 0) {
+				# Mediawiki requires the Category
+				# prefix, but let's not force the user
+				# to specify it.
+				$category = "Category:" . $category;
+			}
+			my $mw_pages = $mediawiki->list( {
+				action => 'query',
+				list => 'categorymembers',
+				cmtitle => $category,
+				cmlimit => 'max' } )
+			    || die $mediawiki->{error}->{code} . ': ' . $mediawiki->{error}->{details};
+			foreach my $page (@{$mw_pages}) {
+				$pages{$page->{title}} = $page;
+			}
+		}
+	}
+	if (!$user_defined) {
+		# No user-provided list, get the list of pages from
+		# the API.
+		my $mw_pages = $mediawiki->list({
+			action => 'query',
+			list => 'allpages',
+			aplimit => 500,
+		});
+		if (!defined($mw_pages)) {
+			print STDERR "fatal: could not get the list of wiki pages.\n";
+			print STDERR "fatal: '$url' does not appear to be a mediawiki\n";
+			print STDERR "fatal: make sure '$url/api.php' is a valid page.\n";
+			exit 1;
+		}
+		foreach my $page (@{$mw_pages}) {
+			$pages{$page->{title}} = $page;
+		}
+	}
+	return values(%pages);
+}
+
+sub run_git {
+	open(my $git, "-|:encoding(UTF-8)", "git " . $_[0]);
+	my $res = do { local $/; <$git> };
+	close($git);
+
+	return $res;
+}
+
+
+sub get_last_local_revision {
+	# Get note regarding last mediawiki revision
+	my $note = run_git("notes --ref=$remotename/mediawiki show refs/mediawiki/$remotename/master 2>/dev/null");
+	my @note_info = split(/ /, $note);
+
+	my $lastrevision_number;
+	if (!(defined($note_info[0]) && $note_info[0] eq "mediawiki_revision:")) {
+		print STDERR "No previous mediawiki revision found";
+		$lastrevision_number = 0;
+	} else {
+		# Notes are formatted : mediawiki_revision: #number
+		$lastrevision_number = $note_info[1];
+		chomp($lastrevision_number);
+		print STDERR "Last local mediawiki revision found is $lastrevision_number";
+	}
+	return $lastrevision_number;
+}
+
+sub get_last_remote_revision {
+	mw_connect_maybe();
+
+	my @pages = get_mw_pages();
+
+	my $max_rev_num = 0;
+
+	foreach my $page (@pages) {
+		my $id = $page->{pageid};
+
+		my $query = {
+			action => 'query',
+			prop => 'revisions',
+			rvprop => 'ids',
+			pageids => $id,
+		};
+
+		my $result = $mediawiki->api($query);
+
+		my $lastrev = pop(@{$result->{query}->{pages}->{$id}->{revisions}});
+
+		$max_rev_num = ($lastrev->{revid} > $max_rev_num ? $lastrev->{revid} : $max_rev_num);
+	}
+
+	print STDERR "Last remote revision found is $max_rev_num.\n";
+	return $max_rev_num;
+}
+
+# Clean content before sending it to MediaWiki
+sub mediawiki_clean {
+	my $string = shift;
+	my $page_created = shift;
+	# Mediawiki does not allow blank space at the end of a page and ends with a single \n.
+	# This function right trims a string and adds a \n at the end to follow this rule
+	$string =~ s/\s+$//;
+	if ($string eq "" && $page_created) {
+		# Creating empty pages is forbidden.
+		$string = EMPTY_CONTENT;
+	}
+	return $string."\n";
+}
+
+# Filter applied on MediaWiki data before adding them to Git
+sub mediawiki_smudge {
+	my $string = shift;
+	if ($string eq EMPTY_CONTENT) {
+		$string = "";
+	}
+	# This \n is important. This is due to mediawiki's way to handle end of files.
+	return $string."\n";
+}
+
+sub mediawiki_clean_filename {
+	my $filename = shift;
+	$filename =~ s/@{[SLASH_REPLACEMENT]}/\//g;
+	# [, ], |, {, and } are forbidden by MediaWiki, even URL-encoded.
+	# Do a variant of URL-encoding, i.e. looks like URL-encoding,
+	# but with _ added to prevent MediaWiki from thinking this is
+	# an actual special character.
+	$filename =~ s/[\[\]\{\}\|]/sprintf("_%%_%x", ord($&))/ge;
+	# If we use the uri escape before
+	# we should unescape here, before anything
+
+	return $filename;
+}
+
+sub mediawiki_smudge_filename {
+	my $filename = shift;
+	$filename =~ s/\//@{[SLASH_REPLACEMENT]}/g;
+	$filename =~ s/ /_/g;
+	# Decode forbidden characters encoded in mediawiki_clean_filename
+	$filename =~ s/_%_([0-9a-fA-F][0-9a-fA-F])/sprintf("%c", hex($1))/ge;
+	return $filename;
+}
+
+sub literal_data {
+	my ($content) = @_;
+	print STDOUT "data ", bytes::length($content), "\n", $content;
+}
+
+sub mw_capabilities {
+	# Revisions are imported to the private namespace
+	# refs/mediawiki/$remotename/ by the helper and fetched into
+	# refs/remotes/$remotename later by fetch.
+	print STDOUT "refspec refs/heads/*:refs/mediawiki/$remotename/*\n";
+	print STDOUT "import\n";
+	print STDOUT "list\n";
+	print STDOUT "push\n";
+	print STDOUT "\n";
+}
+
+sub mw_list {
+	# MediaWiki do not have branches, we consider one branch arbitrarily
+	# called master, and HEAD pointing to it.
+	print STDOUT "? refs/heads/master\n";
+	print STDOUT "\@refs/heads/master HEAD\n";
+	print STDOUT "\n";
+}
+
+sub mw_option {
+	print STDERR "remote-helper command 'option $_[0]' not yet implemented\n";
+	print STDOUT "unsupported\n";
+}
+
+sub fetch_mw_revisions_for_page {
+	my $page = shift;
+	my $id = shift;
+	my $fetch_from = shift;
+	my @page_revs = ();
+	my $query = {
+		action => 'query',
+		prop => 'revisions',
+		rvprop => 'ids',
+		rvdir => 'newer',
+		rvstartid => $fetch_from,
+		rvlimit => 500,
+		pageids => $id,
+	};
+
+	my $revnum = 0;
+	# Get 500 revisions at a time due to the mediawiki api limit
+	while (1) {
+		my $result = $mediawiki->api($query);
+
+		# Parse each of those 500 revisions
+		foreach my $revision (@{$result->{query}->{pages}->{$id}->{revisions}}) {
+			my $page_rev_ids;
+			$page_rev_ids->{pageid} = $page->{pageid};
+			$page_rev_ids->{revid} = $revision->{revid};
+			push(@page_revs, $page_rev_ids);
+			$revnum++;
+		}
+		last unless $result->{'query-continue'};
+		$query->{rvstartid} = $result->{'query-continue'}->{revisions}->{rvstartid};
+	}
+	if ($shallow_import && @page_revs) {
+		print STDERR "  Found 1 revision (shallow import).\n";
+		@page_revs = sort {$b->{revid} <=> $a->{revid}} (@page_revs);
+		return $page_revs[0];
+	}
+	print STDERR "  Found ", $revnum, " revision(s).\n";
+	return @page_revs;
+}
+
+sub fetch_mw_revisions {
+	my $pages = shift; my @pages = @{$pages};
+	my $fetch_from = shift;
+
+	my @revisions = ();
+	my $n = 1;
+	foreach my $page (@pages) {
+		my $id = $page->{pageid};
+
+		print STDERR "page $n/", scalar(@pages), ": ". $page->{title} ."\n";
+		$n++;
+		my @page_revs = fetch_mw_revisions_for_page($page, $id, $fetch_from);
+		@revisions = (@page_revs, @revisions);
+	}
+
+	return ($n, @revisions);
+}
+
+sub import_file_revision {
+	my $commit = shift;
+	my %commit = %{$commit};
+	my $full_import = shift;
+	my $n = shift;
+
+	my $title = $commit{title};
+	my $comment = $commit{comment};
+	my $content = $commit{content};
+	my $author = $commit{author};
+	my $date = $commit{date};
+
+	print STDOUT "commit refs/mediawiki/$remotename/master\n";
+	print STDOUT "mark :$n\n";
+	print STDOUT "committer $author <$author\@$wiki_name> ", $date->epoch, " +0000\n";
+	literal_data($comment);
+
+	# If it's not a clone, we need to know where to start from
+	if (!$full_import && $n == 1) {
+		print STDOUT "from refs/mediawiki/$remotename/master^0\n";
+	}
+	if ($content ne DELETED_CONTENT) {
+		print STDOUT "M 644 inline $title.mw\n";
+		literal_data($content);
+		print STDOUT "\n\n";
+	} else {
+		print STDOUT "D $title.mw\n";
+	}
+
+	# mediawiki revision number in the git note
+	if ($full_import && $n == 1) {
+		print STDOUT "reset refs/notes/$remotename/mediawiki\n";
+	}
+	print STDOUT "commit refs/notes/$remotename/mediawiki\n";
+	print STDOUT "committer $author <$author\@$wiki_name> ", $date->epoch, " +0000\n";
+	literal_data("Note added by git-mediawiki during import");
+	if (!$full_import && $n == 1) {
+		print STDOUT "from refs/notes/$remotename/mediawiki^0\n";
+	}
+	print STDOUT "N inline :$n\n";
+	literal_data("mediawiki_revision: " . $commit{mw_revision});
+	print STDOUT "\n\n";
+}
+
+# parse a sequence of
+# <cmd> <arg1>
+# <cmd> <arg2>
+# \n
+# (like batch sequence of import and sequence of push statements)
+sub get_more_refs {
+	my $cmd = shift;
+	my @refs;
+	while (1) {
+		my $line = <STDIN>;
+		if ($line =~ m/^$cmd (.*)$/) {
+			push(@refs, $1);
+		} elsif ($line eq "\n") {
+			return @refs;
+		} else {
+			die("Invalid command in a '$cmd' batch: ". $_);
+		}
+	}
+}
+
+sub mw_import {
+	# multiple import commands can follow each other.
+	my @refs = (shift, get_more_refs("import"));
+	foreach my $ref (@refs) {
+		mw_import_ref($ref);
+	}
+	print STDOUT "done\n";
+}
+
+sub mw_import_ref {
+	my $ref = shift;
+	# The remote helper will call "import HEAD" and
+	# "import refs/heads/master".
+	# Since HEAD is a symbolic ref to master (by convention,
+	# followed by the output of the command "list" that we gave),
+	# we don't need to do anything in this case.
+	if ($ref eq "HEAD") {
+		return;
+	}
+
+	mw_connect_maybe();
+
+	my @pages = get_mw_pages();
+
+	print STDERR "Searching revisions...\n";
+	my $last_local = get_last_local_revision();
+	my $fetch_from = $last_local + 1;
+	if ($fetch_from == 1) {
+		print STDERR ", fetching from beginning.\n";
+	} else {
+		print STDERR ", fetching from here.\n";
+	}
+	my ($n, @revisions) = fetch_mw_revisions(\@pages, $fetch_from);
+
+	# Creation of the fast-import stream
+	print STDERR "Fetching & writing export data...\n";
+
+	$n = 0;
+	my $last_timestamp = 0; # Placeholer in case $rev->timestamp is undefined
+
+	foreach my $pagerevid (sort {$a->{revid} <=> $b->{revid}} @revisions) {
+		# fetch the content of the pages
+		my $query = {
+			action => 'query',
+			prop => 'revisions',
+			rvprop => 'content|timestamp|comment|user|ids',
+			revids => $pagerevid->{revid},
+		};
+
+		my $result = $mediawiki->api($query);
+
+		my $rev = pop(@{$result->{query}->{pages}->{$pagerevid->{pageid}}->{revisions}});
+
+		$n++;
+
+		my %commit;
+		$commit{author} = $rev->{user} || 'Anonymous';
+		$commit{comment} = $rev->{comment} || '*Empty MediaWiki Message*';
+		$commit{title} = mediawiki_smudge_filename(
+			$result->{query}->{pages}->{$pagerevid->{pageid}}->{title}
+		    );
+		$commit{mw_revision} = $pagerevid->{revid};
+		$commit{content} = mediawiki_smudge($rev->{'*'});
+
+		if (!defined($rev->{timestamp})) {
+			$last_timestamp++;
+		} else {
+			$last_timestamp = $rev->{timestamp};
+		}
+		$commit{date} = DateTime::Format::ISO8601->parse_datetime($last_timestamp);
+
+		print STDERR "$n/", scalar(@revisions), ": Revision #$pagerevid->{revid} of $commit{title}\n";
+
+		import_file_revision(\%commit, ($fetch_from == 1), $n);
+	}
+
+	if ($fetch_from == 1 && $n == 0) {
+		print STDERR "You appear to have cloned an empty MediaWiki.\n";
+		# Something has to be done remote-helper side. If nothing is done, an error is
+		# thrown saying that HEAD is refering to unknown object 0000000000000000000
+		# and the clone fails.
+	}
+}
+
+sub error_non_fast_forward {
+	# Native git-push would show this after the summary.
+	# We can't ask it to display it cleanly, so print it
+	# ourselves before.
+	print STDERR "To prevent you from losing history, non-fast-forward updates were rejected\n";
+	print STDERR "Merge the remote changes (e.g. 'git pull') before pushing again. See the\n";
+	print STDERR "'Note about fast-forwards' section of 'git push --help' for details.\n";
+
+	print STDOUT "error $_[0] \"non-fast-forward\"\n";
+	return 0;
+}
+
+sub mw_push_file {
+	my $diff_info = shift;
+	# $diff_info contains a string in this format:
+	# 100644 100644 <sha1_of_blob_before_commit> <sha1_of_blob_now> <status>
+	my @diff_info_split = split(/[ \t]/, $diff_info);
+
+	# Filename, including .mw extension
+	my $complete_file_name = shift;
+	# Commit message
+	my $summary = shift;
+
+	my $new_sha1 = $diff_info_split[3];
+	my $old_sha1 = $diff_info_split[2];
+	my $page_created = ($old_sha1 eq NULL_SHA1);
+	my $page_deleted = ($new_sha1 eq NULL_SHA1);
+	$complete_file_name = mediawiki_clean_filename($complete_file_name);
+
+	if (substr($complete_file_name,-3) eq ".mw") {
+		my $title = substr($complete_file_name,0,-3);
+
+		my $file_content;
+		if ($page_deleted) {
+			# Deleting a page usually requires
+			# special priviledges. A common
+			# convention is to replace the page
+			# with this content instead:
+			$file_content = DELETED_CONTENT;
+		} else {
+			$file_content = run_git("cat-file blob $new_sha1");
+		}
+
+		mw_connect_maybe();
+
+		my $result = $mediawiki->edit( {
+			action => 'edit',
+			summary => $summary,
+			title => $title,
+			text => mediawiki_clean($file_content, $page_created),
+				  }, {
+					  skip_encoding => 1 # Helps with names with accentuated characters
+				  }) || die 'Fatal: Error ' .
+				  $mediawiki->{error}->{code} .
+				  ' from mediwiki: ' . $mediawiki->{error}->{details};
+		print STDERR "Pushed file : $new_sha1 - $title\n";
+	} else {
+		print STDERR "$complete_file_name not a mediawiki file (Not pushable on this version of git-remote-mediawiki).\n"
+	}
+}
+
+sub mw_push {
+	# multiple push statements can follow each other
+	my @refsspecs = (shift, get_more_refs("push"));
+	my %status;
+	my $pushed;
+	for my $refspec (@refsspecs) {
+		my ($force, $local, $remote) = $refspec =~ /^(\+)?([^:]*):([^:]*)$/
+		    or die("Invalid refspec for push. Expected <src>:<dst> or +<src>:<dst>");
+		if ($force) {
+			print STDERR "Warning: forced push not allowed on a MediaWiki.\n";
+		}
+		if ($local eq "") {
+			print STDERR "Cannot delete remote branch on a MediaWiki\n";
+			print STDOUT "error $remote cannot delete\n";
+			next;
+		}
+		if ($remote ne "refs/heads/master") {
+			print STDERR "Only push to the branch 'master' is supported on a MediaWiki\n";
+			print STDOUT "error $remote only master allowed\n";
+			next;
+		}
+		if (mw_push_revision($local, $remote)) {
+			$pushed = 1;
+		}
+	}
+
+	# Notify Git that the push is done
+	print STDOUT "\n";
+
+	if ($pushed) {
+		print STDERR "Just pushed some revisions to MediaWiki.\n";
+		print STDERR "The pushed revisions now have to be re-imported, and your current branch\n";
+		print STDERR "needs to be updated with these re-imported commits. You can do this with\n";
+		print STDERR "\n";
+		print STDERR "  git pull --rebase\n";
+		print STDERR "\n";
+	}
+}
+
+sub mw_push_revision {
+	my $local = shift;
+	my $remote = shift; # actually, this has to be "refs/heads/master" at this point.
+	my $last_local_revid = get_last_local_revision();
+	print STDERR ".\n"; # Finish sentence started by get_last_local_revision()
+	my $last_remote_revid = get_last_remote_revision();
+
+	# Get sha1 of commit pointed by local HEAD
+	my $HEAD_sha1 = run_git("rev-parse $local 2>/dev/null"); chomp($HEAD_sha1);
+	# Get sha1 of commit pointed by remotes/$remotename/master
+	my $remoteorigin_sha1 = run_git("rev-parse refs/remotes/$remotename/master 2>/dev/null");
+	chomp($remoteorigin_sha1);
+
+	if ($last_local_revid > 0 &&
+	    $last_local_revid < $last_remote_revid) {
+		return error_non_fast_forward($remote);
+	}
+
+	if ($HEAD_sha1 eq $remoteorigin_sha1) {
+		# nothing to push
+		return 0;
+	}
+
+	# Get every commit in between HEAD and refs/remotes/origin/master,
+	# including HEAD and refs/remotes/origin/master
+	my @commit_pairs = ();
+	if ($last_local_revid > 0) {
+		my $parsed_sha1 = $remoteorigin_sha1;
+		# Find a path from last MediaWiki commit to pushed commit
+		while ($parsed_sha1 ne $HEAD_sha1) {
+			my @commit_info =  grep(/^$parsed_sha1/, split(/\n/, run_git("rev-list --children $local")));
+			if (!@commit_info) {
+				return error_non_fast_forward($remote);
+			}
+			my @commit_info_split = split(/ |\n/, $commit_info[0]);
+			# $commit_info_split[1] is the sha1 of the commit to export
+			# $commit_info_split[0] is the sha1 of its direct child
+			push(@commit_pairs, \@commit_info_split);
+			$parsed_sha1 = $commit_info_split[1];
+		}
+	} else {
+		# No remote mediawiki revision. Export the whole
+		# history (linearized with --first-parent)
+		print STDERR "Warning: no common ancestor, pushing complete history\n";
+		my $history = run_git("rev-list --first-parent --children $local");
+		my @history = split('\n', $history);
+		@history = @history[1..$#history];
+		foreach my $line (reverse @history) {
+			my @commit_info_split = split(/ |\n/, $line);
+			push(@commit_pairs, \@commit_info_split);
+		}
+	}
+
+	foreach my $commit_info_split (@commit_pairs) {
+		my $sha1_child = @{$commit_info_split}[0];
+		my $sha1_commit = @{$commit_info_split}[1];
+		my $diff_infos = run_git("diff-tree -r --raw -z $sha1_child $sha1_commit");
+		# TODO: we could detect rename, and encode them with a #redirect on the wiki.
+		# TODO: for now, it's just a delete+add
+		my @diff_info_list = split(/\0/, $diff_infos);
+		# Keep the first line of the commit message as mediawiki comment for the revision
+		my $commit_msg = (split(/\n/, run_git("show --pretty=format:\"%s\" $sha1_commit")))[0];
+		chomp($commit_msg);
+		# Push every blob
+		while (@diff_info_list) {
+			# git diff-tree -z gives an output like
+			# <metadata>\0<filename1>\0
+			# <metadata>\0<filename2>\0
+			# and we've split on \0.
+			my $info = shift(@diff_info_list);
+			my $file = shift(@diff_info_list);
+			mw_push_file($info, $file, $commit_msg);
+		}
+	}
+
+	print STDOUT "ok $remote\n";
+	return 1;
+}
diff --git a/contrib/mw-to-git/git-remote-mediawiki.txt b/contrib/mw-to-git/git-remote-mediawiki.txt
new file mode 100644
index 0000000000..4d211f5b81
--- /dev/null
+++ b/contrib/mw-to-git/git-remote-mediawiki.txt
@@ -0,0 +1,7 @@
+Git-Mediawiki is a project which aims the creation of a gate
+between git and mediawiki, allowing git users to push and pull
+objects from mediawiki just as one would do with a classic git
+repository thanks to remote-helpers.
+
+For more information, visit the wiki at
+https://github.com/Bibzball/Git-Mediawiki/wiki