#!/bin/sh

setvar USAGE = ""[-a] [-r] [-m] [-t] [-n] [-b <newname>] <name>""
setvar 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.""

setvar OPTIONS_KEEPDASHDASH = ''
setvar OPTIONS_STUCKLONG = ''
setvar 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
	)
}

setvar _x40 = ""[0-9a-f][0-9a-f][0-9a-f][0-9a-f][0-9a-f]""
setvar _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} "
}

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

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

test "$Argc" = 1 || usage

setvar 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"
}

setvar branch = "$1"
test -z $new_name && setvar new_name = "$branch"

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

setvar candidates = "$(git rev-parse $candidates | sort -u)"

if test -z $candidates {
	setvar hint = ''
	test "z$all_strategies" != "ztttt" \
		&& setvar 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-

setvar 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"
}