cg-object-id

#!/usr/bin/env bash
#
# Get the SHA1 id of an object associated with the given symbolic id
# Copyright (c) Petr Baudis, Pavel Roskin, Philip Pokorny  2005
#
# Resolves a given symbolic id to the raw SHA1 id (or a symbolic
# description when passed the '-d' parameter). The symbolic id can be
# an SHA1 id, a unique starting segment of an existing SHA1 id, a ref
# name, date, empty string, etc. See the 'COMMIT_ID' description in
# cogito(7) for the full list.
#
# Normally, you do not use this command directly (except with the '-d'
# parameter), but it is used in other Cogito scripts to resolve passed
# object identifiers. If the ID is not provided, HEAD is assumed.  The
# default behavior is to show the commit ID, but you should always
# explicitly write '-c' if using this in a script.
#
# OPTIONS
# -------
# -b:: Get branch name
#	Get name of the current branch.
#
# -c:: Get commit ID
#	Get ID of commit matching the object ID (error out if it is not
#	a commit). This is the default if you do not pass any parameter
#	as well, but that is only for the human usage. For clarity, all
#	scripted usage of cg-object-id should use -c explicitly if it
#	wants a commit.
#
# -d:: Get commit string description
#	Get a commit description in form of a short string. It shows the
#	most recent tag in past of the commit and if it is not the commit
#	itself, it appends first few chars of the commit id to id. See
#	`git-describe`(1) for details.
#
# -n:: Disable object type checking
#	Normalize only - don't check the object type.
#
# -p:: Get parent commit ID(s)
#	Get ID of the first parent commit of a given revision or HEAD.
#	NOTE: Multiple SHA1s separated by newlines will be returned for
#	commits with multiple parents.
#
# -t:: Get tree ID
#	Get ID of tree associated with given commit or HEAD.
#
# OBJECT_ID::
#	An ID resolving to a commit.

# Testsuite: Partial (used in many tests but a dedicated testsuite is missing)

USAGE="cg-object-id [-b | -c | -d | -n | -p | -t] [OBJECT_ID]"
_git_wc_unneeded=1

. "${COGITO_LIB}"cg-Xlib


# Normalize argument.  The normalized SHA1 ID is put to $normid,
# type is put to $type.
normalize_id()
{
	local id="$1"
	local revid=
	local valid=

	if [ ! "$id" ] || [ "$id" = "this" ]; then
		id=HEAD;
	fi

	revid="$(git-rev-parse --verify "$id" 2>/dev/null)"
	if [ "$revid" ] && [ ${#revid} -eq 40 ] && [ "${revid//[0-9a-f]/}" = "" ]; then
		id="$revid"
		valid=1
	fi

	# date does the wrong thing for empty and single-letter ids
	if [ ${#id} -gt 1 ] && [ ! "$valid" ]; then
		reqsecs="$(date --date="$id" +'%s' 2>/dev/null)"

		if [ "$reqsecs" ]; then
			revid="$(git-rev-list "--min-age=$reqsecs" --max-count=1 HEAD)"
			if [ "$revid" ]; then
				id="$revid"
				valid=1
			fi
		fi
	fi

	# If we don't have a 40-char ID by now, it's an error
	if [ ! "$valid" ]; then
		echo "Invalid id: $id" >&2
		exit 1
	fi

	type="$(git-cat-file -t "$id")"
	if [ "$type" = "tag" ]; then
		id="$(git-cat-file tag "$id" | head -n 1)"
		id="${id#object }"
		type=
	fi

	normid="$id"
}



show_commit= # this is really only for the options-exclusivity-checking
describe=
show_parent=
show_tree=
normalize_only=
while optparse; do
	if optparse -b; then
		# one-shot
		echo "$_git_head"
		exit
	elif optparse -c; then
		show_commit=1
	elif optparse -d; then
		describe=1
	elif optparse -n; then
		normalize_only=1
	elif optparse -p; then
		show_parent=1
	elif optparse -t; then
		show_tree=1
	else
		optfail
	fi
done

# Compatibility code
case "$_cg_cmd" in
	*parent*) show_parent=1;;
	*tree*) show_tree=1;;
esac

case "$show_commit$describe$show_parent$show_tree$normalize_only" in
	11*)	usage;;
esac

id="${ARGS[0]}"
normalize_id "$id"

if [ "$normalize_only" ]; then
	echo "$normid"
	exit 0
fi
if [ "$describe" ]; then
	git-describe "$normid"
	exit 0
fi


if [ "$show_parent" ]; then
	git-rev-list --parents -n 1 "$normid" | tr ' ' '\n' | tail -n +2
	exit 0
fi

[ "$type" ] || type="$(git-cat-file -t "$normid")"
if [ "$show_tree" ]; then
	if [ "$type" = "commit" ]; then
		normid="$(git-cat-file commit "$normid" | sed -e 's/tree //;q')"
		type="$(git-cat-file -t "$normid")"
	fi

	if [ "$type" != "tree" ]; then
		echo "Invalid tree id: $normid" >&2
		exit 1
	fi
else
	if [ "$type" != "commit" ]; then
		echo "Invalid commit id: $normid" >&2
		exit 1
	fi
fi

echo "$normid"