Import git9 from mercurial repository

LICENSE

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+Copyright (c) 2019 Ori Bernstein
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.

README

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+Git for Plan 9: git/fs
+======================
+
+Plan 9 is a non-posix system that currently has no git port.  Git
+itself feels distinctly un-plan9ish.
+
+Git/fs implements a git client for plan 9.  The intent is to support
+working with git repositories, without cloning the git interface
+directly.
+
+Git/fs is alpha software. It more or less works for me, but has many
+bugs, and many more missing tools, but it's at the point where the
+hard parts are done, and "the rest is just scripting", using standard
+command line tools (cp, echo, diff, patch, and diff3).
+
+Structure
+---------
+
+The git/fs program provides a file system mounted on /mnt/git.  It
+provides a read-only view into the repository contents to allow
+scripts to inspect the data.  Surrounding scripts and binaries will
+manipulate the repository contents directly.  These changes will be
+immediately mirrored in the file system.
+
+Scripts will generally mount git/fs as needed to do
+their work, but if you want to browse the repository
+manually, run it yourself. You'll get `/mnt/git` mounted,
+with the following contents:
+
+	/mnt/git/object:	The objects in the repo.
+	/mnt/git/branch:	The branches in the repo.
+	/mnt/git/ctl:		A file showing the status of the repo.
+				Currently, it only shows the current branch.
+	/mnt/git/HEAD		An alias for the currently checked out
+				commit directory.
+
+Visible Differences
+-------------------
+
+The most obvious difference is that Git's index is a bit boneheaded, so I'm
+ignoring it.  The index doesn't affect the wire protocol, so this
+isn't an interoperability issue, unless you share the same physical
+repository on both Plan 9 and Unix.  If you do, expect them to disagree
+about the files that have been modified in the working copy.
+
+In fact, the entire concept of the staging area has been dropped, as
+it's both confusing and clunky.  There are now only three states that
+files can be in: 'untracked', 'dirty', and 'committed'.  Tracking is
+done with empty files under .git/index9/{removed,tracked}/path/to/file.
+
+It's implemented in Plan 9 flavor C, and provides tools for writing
+repository contents, and a file system for read-only access, which
+will mirror the current state of the repository.
+
+Installation
+------------
+
+Install with `mk install`.
+
+Examples
+--------
+
+Some usage examples:
+
+	git/clone git://git.eigenstate.org/ori/mc.git
+	git/log
+	cd subdir/name
+	git/add foo.c
+	diff bar.c /mnt/git/HEAD/
+	git/commit
+	git/push
+
+Commits are presented as directories with the following
+contents:
+
+	author:	A file containing the author name
+	hash:	A file containing the commit hash
+	parent:	A file containing the commit parents, one per line.
+	msg:	A file containing the log message for that commit
+	tree:	A directory containing a view of the repository.
+
+So, for example:
+
+	% ls /mnt/git/branch/heads/master
+	/mnt/git/branch/heads/master/author
+	/mnt/git/branch/heads/master/hash
+	/mnt/git/branch/heads/master/msg
+	/mnt/git/branch/heads/master/parent
+	/mnt/git/branch/heads/master/tree
+	% cat /mnt/git/branch/heads/master/hash
+	7d539a7c08aba3f31b3913e0efef11c43ea9
+
+	# This is the same commit, with the same contents.
+	% ls /mnt/git/object/7d539a7c08aba3f31b3913e0efef11c43ea9f9ef
+	/mnt/git/object/7d539a7c08aba3f31b3913e0efef11c43ea9f9ef/author
+	/mnt/git/object/7d539a7c08aba3f31b3913e0efef11c43ea9f9ef/hash
+	/mnt/git/object/7d539a7c08aba3f31b3913e0efef11c43ea9f9ef/msg
+	/mnt/git/object/7d539a7c08aba3f31b3913e0efef11c43ea9f9ef/parent
+	/mnt/git/object/7d539a7c08aba3f31b3913e0efef11c43ea9f9ef/tree
+
+	# what git/diff will hopefully do more concisely soon, filtering
+	# out the non-git files.
+	ape/diff -ur /mnt/git/branch/heads/master/tree .
+	Only in .: .git
+	Only in .: debug
+	diff -ur /mnt/git/branch/heads/master/tree/fold.myr ./fold.myr
+	--- /mnt/git/branch/heads/master/tree/fold.myr	Wed Dec 31 16:00:00 1969
+	+++ ./fold.myr	Mon Apr  1 21:39:06 2019
+	@@ -6,6 +6,8 @@
+	 	const foldexpr : (e : expr# -> std.option(constval))
+	 ;;
+
+	+/* Look, diffing files just works, and I don't need any fancy glue! */
+	+
+	 const foldexpr = {e
+	 	match e
+	 	| &(`Eident &[.sc=`Sclassenum, .name=name, .ty=`Tyenum &(`Body enum)]):
+	Only in .: refs
+
+
+The following utilities and binaries are provided:
+
+	fs:	The git filesystem.
+	fetch:	The protocol bits for getting data from a git server.
+	send:	The protocol bits for sending data to a git server.
+	save:	The gnarly bits for storing the files for a commit.
+	conf:	A program to extract information from a config file.
+	clone:	Clones a repository.
+	commit:	Commits a snapshot of the working directory.
+	log:	Prints the contents of a commmit log.
+	add:	Tells the repository to add a file to the next commit.
+	walk:	`du`, but for git status.
+
+
+Supported protocols: git:// and git+ssh://. If someone
+implements others, I'll gladly accept patches.
+
+TODOs
+-----
+
+Documentation has not yet been written.  You'll need to read the
+source. Notably missing functionality includes:
+
+	git/mkpatch:	Generate a 'git am' compatible patch.
+	git/apply:	Apply a diff.
+	git/diff:	Wrapper wrapper around git/walk that
+			diffs the changed files.
+	git/merge:	Yup, what it says on the label. Should
+			also be a script around git/fs.
+	git/log:	Need to figure out how to make it filter
+			by files.

add

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+#!/bin/rc -e
+
+rfork ne
+
+fn usage {
+	echo 'usage: '$argv0' [-r] files..' >[1=2]
+	echo '	-r:		remove instead of adding' >[1=2]
+}
+
+add='tracked'
+del='removed'
+while(~ $1 -*){
+	switch($1){
+	case -r
+		add='removed'
+		del='tracked'
+	case --
+		break
+	case *; usage
+	}
+	shift
+}
+
+dir=`{pwd}
+base=`{git/conf -r}
+if(! ~ $status ''){
+	echo 'not in git repository' `{pwd} >[1=2]
+	exit notrepo
+}
+
+cd $base
+rel=`{sed 's@^'$base'/*@@' <{echo $dir}}
+if(~ $#rel 0)
+	rel=''
+for(f in $*){
+	if(! test -f $base/$rel/$f){
+		echo 'could not add '$base/$rel/$f': does not exist' >[1=2]
+		exit 'nofile'
+	}
+	addpath=.git/index9/$add/$rel/$f
+	delpath=.git/index9/$del/$rel/$f
+	mkdir -p `{basename -d $addpath}
+	mkdir -p `{basename -d $delpath}
+	touch $addpath
+	rm -f $delpath
+}

branch

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+#!/bin/rc -e
+
+rfork en
+
+fn usage{
+	echo usage: $argv0 [-b base] [-o origin] new >[2=1]
+	echo '	'-b base:	use "base" for branch (default: current branch) >[2=1]
+	echo '	'-o origin:	use "origin" for remote branch >[2=1]
+	echo '	'new:		name of new branch
+	exit usage
+}
+
+if(! cd `{git/conf -r}){
+	exit 'not in git repository'
+	exit notgit
+}
+git/fs
+
+nl='
+'
+stay=''
+create=''
+cur=`{awk '$1=="branch"{print $2}' < /mnt/git/ctl}
+while(~ $1 -* && ! ~ $1 --){
+	switch($1){
+	case -c; create=true
+	case -s; stay=true
+	case -o; origin=$1
+	case *; usage
+	}
+	shift
+}
+if(~ $1 --) shift
+
+if(~ $#* 0){
+	echo $cur
+	exit
+}
+if(! ~ $#* 1)
+	usage
+new=$1
+
+if(~ $create ''){
+	if(! test -e .git/refs/heads/$new){
+		echo branch $new: does not exist >[1=2]
+		exit exists
+	}
+}
+if not{
+	if(test -e .git/refs/heads/$new){
+		echo could not create $new: already exists >[1=2]
+		exit exists
+	}
+	branched=''
+	candidates=(.git/refs/$cur .git/refs/heads/$cur .git/refs/remotes/$cur .git/refs/remotes/*/$cur)
+	for(br in $candidates){
+		if(test -f $br){
+			echo 'creating new branch '$new
+			cp $br .git/refs/heads/$new
+			branched="ok"
+		}
+	}
+	if(~ $branched ''){
+		echo 'could not find branch '$cur >[1=2]
+		exit notfound
+	}
+}
+
+if(~ $stay ''){
+	rm -f `$nl{git/walk -cfT}
+	echo 'ref: refs/heads/'$new > .git/HEAD
+	tree=/mnt/git/HEAD/tree
+	@{builtin cd $tree && tar cif /fd/1 .} | @{tar xf /fd/0}
+	for(f in `$nl{walk -f $tree | sed 's@^'$tree'/*@@'}){
+		if(! ~ $#f 0){
+			idx=.git/index9/tracked/$f
+			mkdir -p `{basename -d $idx}
+			walk -eq $f > $idx
+		}
+	}
+}

clone

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+#!/bin/rc
+
+rfork en
+nl='
+'
+
+if(~ $#* 1){
+	remote=$1
+	local=`{basename $1 .git}
+}
+if not if(~ $#* 2){
+	remote=$1
+	local=$2
+}
+if not{
+	echo usage: git/clone remote [local] >[1=2]
+	exit usage
+}
+
+if(test -e $local){
+	echo $local already exists
+	exit exists
+}
+	
+fn clone{
+	mkdir -p $local/.git
+	mkdir -p $local/.git/objects/pack/
+	mkdir -p $local/.git/refs/heads/
+	
+	cd $local
+	
+	dircp /sys/lib/git/template .git
+	echo '[remote "origin"]' 				>> .git/config
+	echo '	url='$remote					>> .git/config
+	echo '	fetch=+refs/heads/*:refs/remotes/origin/*'	>> .git/config
+	{git/fetch $remote >[2=3] | awk '
+		/^remote/{
+			if($2=="HEAD"){
+				headhash=$3
+				headref=""
+			}else{
+				gsub("^refs/heads", "refs/remotes/origin", $2)
+				if($2 == "refs/remotes/origin/master" || $3 == headhash)
+					headref=$2
+				outfile = ".git/" $2
+				system("mkdir -p `{basename -d "outfile"}")
+				print $3 > outfile
+				close(outfile)
+			}
+		}
+		END{
+			if(headref != ""){
+				remote = headref
+				gsub("^refs/remotes/origin", "refs/heads", headref)
+				system("mkdir -p `{basename -d .git/" headref"}");
+				system("cp .git/" remote " .git/" headref)
+				print "ref: " headref > ".git/HEAD"
+			}else{
+				print "warning: detached head "headhash > "/fd/2"
+				print headhash > ".git/HEAD"
+			}
+		}
+	'} |[3] tr '\x0d' '\x0a'
+	if(! ~ $status '|')
+		exit 'clone:' $status
+
+	tree=/mnt/git/branch/heads/master/tree
+	echo checking out repository...
+	if(test -f .git/refs/remotes/origin/master){
+		cp .git/refs/remotes/origin/master .git/refs/heads/master
+		git/fs
+		@ {builtin cd $tree && tar cif /fd/1 .} | @ {tar xf /fd/0}
+		if(! ~ $status '')
+			exit 'checkout:' $status
+		for(f in `$nl{walk -f $tree | sed 's@^'$tree'/*@@'}){
+			if(! ~ $#f 0){
+				idx=.git/index9/tracked/$f
+				mkdir -p `{basename -d $idx}
+				walk -eq $f > $idx
+			}
+		}
+	}
+	if not{
+		echo no master branch >[1=2]
+		echo check out your code with git/branch >[1=2]
+	}
+}
+
+@{clone}
+st=$status
+if(~ $st ''){
+	echo done.
+}
+if not{
+	echo clone failed: $st >[2=1]
+	echo cleaning up $local >[2=1]
+	rm -rf $local
+}