#!/bin/sh

setglobal USAGE = '"[-a] [-r] [-m] [-t] [-n] [-b <newname>] <name>'"
setglobal LONG_USAGE = '"git-resurrect attempts to find traces of a branch tip
called <name>, and tries to resurrect it.  Currently, the reflog is
searched for checkout messages, and with -r also merge messages.  With
-m and -t, the history of all refs is scanned for Merge <name> into
other/Merge <other> into <name> (respectively) commit subjects, which
is rather slow but allows you to resurrect other people's topic
branches.'"

setglobal OPTIONS_KEEPDASHDASH = ''
setglobal OPTIONS_STUCKLONG = ''
setglobal OPTIONS_SPEC = ""\
git resurrect $USAGE
--
b,branch=            save branch as <newname> instead of <name>
a,all                same as -l -r -m -t
k,keep-going         full rev-list scan (instead of first match)
l,reflog             scan reflog for checkouts (enabled by default)
r,reflog-merges      scan for merges recorded in reflog
m,merges             scan for merges into other branches (slow)
t,merge-targets      scan for merges of other branches into <name>
n,dry-run            don't recreate the branch""

source git-sh-setup

proc search_reflog {
        sed -ne 's~^\([^ ]*\) .*\tcheckout: moving from '"$1"' .*~\1~p' \
                < "$GIT_DIR"/logs/HEAD
}

proc search_reflog_merges {
	git rev-parse $[
		sed -ne 's~^[^ ]* \([^ ]*\) .*\tmerge '"$1"':.*~\1^2~p' \
			< "$GIT_DIR"/logs/HEAD]
}

setglobal _x40 = '"[0-9a-f][0-9a-f][0-9a-f][0-9a-f][0-9a-f]'"
setglobal _x40 = ""$_x40$_x40$_x40$_x40$_x40$_x40$_x40$_x40""

proc search_merges {
        git rev-list --all --grep="Merge branch '$1'" \
                --pretty=tformat:"%P %s" |
        sed -ne "/^$_x40 \($_x40\) Merge .*/ {s//\1/p;$early_exit}"
}

proc search_merge_targets {
	git rev-list --all --grep="Merge branch '[^']*' into $branch\$" \
		--pretty=tformat:"%H %s" --all |
	sed -ne "/^\($_x40\) Merge .*/ {s//\1/p;$early_exit} "
}

setglobal dry_run = ''
setglobal early_exit = 'q'
setglobal scan_reflog = 't'
setglobal scan_reflog_merges = ''
setglobal scan_merges = ''
setglobal scan_merge_targets = ''
setglobal new_name = ''

while test "$Argc" != 0 {
	match $1 {
	    with -b|--branch
		shift
		setglobal new_name = $1
		
	    with -n|--dry-run
		setglobal dry_run = 't'
		
	    with --no-dry-run
		setglobal dry_run = ''
		
	    with -k|--keep-going
		setglobal early_exit = ''
		
	    with --no-keep-going
		setglobal early_exit = 'q'
		
	    with -m|--merges
		setglobal scan_merges = 't'
		
	    with --no-merges
		setglobal scan_merges = ''
		
	    with -l|--reflog
		setglobal scan_reflog = 't'
		
	    with --no-reflog
		setglobal scan_reflog = ''
		
	    with -r|--reflog_merges
		setglobal scan_reflog_merges = 't'
		
	    with --no-reflog_merges
		setglobal scan_reflog_merges = ''
		
	    with -t|--merge-targets
		setglobal scan_merge_targets = 't'
		
	    with --no-merge-targets
		setglobal scan_merge_targets = ''
		
	    with -a|--all
		setglobal scan_reflog = 't'
		setglobal scan_reflog_merges = 't'
		setglobal scan_merges = 't'
		setglobal scan_merge_targets = 't'
		
	    with --
		shift
		break
		
	    with *
		usage
		
	}
	shift
}

test "$Argc" = 1 || usage

setglobal all_strategies = ""$scan_reflog$scan_reflog_merges$scan_merges$scan_merge_targets""
if test -z $all_strategies {
	die "must enable at least one of -lrmt"
}

setglobal branch = $1
test -z $new_name && setglobal new_name = $branch

if test ! -z $scan_reflog {
	if test -r "$GIT_DIR"/logs/HEAD {
		setglobal candidates = $[search_reflog $branch]
	} else {
		die 'reflog scanning requested, but' \
			'$GIT_DIR/logs/HEAD not readable'
	}
}
if test ! -z $scan_reflog_merges {
	if test -r "$GIT_DIR"/logs/HEAD {
		setglobal candidates = ""$candidates $[search_reflog_merges $branch]""
	} else {
		die 'reflog scanning requested, but' \
			'$GIT_DIR/logs/HEAD not readable'
	}
}
if test ! -z $scan_merges {
	setglobal candidates = ""$candidates $[search_merges $branch]""
}
if test ! -z $scan_merge_targets {
	setglobal candidates = ""$candidates $[search_merge_targets $branch]""
}

setglobal candidates = $[git rev-parse $candidates | sort -u]

if test -z $candidates {
	setglobal hint = ''
	test "z$all_strategies" != "ztttt" \
		&& setglobal hint = '" (maybe try again with -a)'"
	die "no candidates for $branch found$hint"
}

echo "** Candidates for $branch **"
for cmt in [$candidates] {
	git --no-pager log --pretty=tformat:"%ct:%h [%cr] %s" --abbrev-commit -1 $cmt
} \
| sort -n | cut -d: -f2-

setglobal newest = $[git rev-list -1 $candidates]
if test ! -z $dry_run {
	printf "** Most recent: "
	git --no-pager log -1 --pretty=tformat:"%h %s" $newest
} elif ! git rev-parse --verify --quiet $new_name >/dev/null {
	printf "** Restoring $new_name to "
	git --no-pager log -1 --pretty=tformat:"%h %s" $newest
	git branch $new_name $newest
} else {
	printf "Most recent: "
	git --no-pager log -1 --pretty=tformat:"%h %s" $newest
	echo "** $new_name already exists, doing nothing"
}