git-checkout: revert specific paths to either index or a given tree-ish.

When extra paths arguments are given, git-checkout reverts only those
paths to either the version recorded in the index or the version
recorded in the given tree-ish.

This has been on the TODO list for quite a while.

Signed-off-by: Junio C Hamano <junkio@cox.net>

1 files changed, 64 insertions, 15 deletions

diff --git a/git-checkout.sh b/git-checkout.sh
index 2c053a33c..73652fa5f 100755
--- a/git-checkout.sh
+++ b/git-checkout.sh
@@ -23,32 +23,81 @@ while [ "$#" != "0" ]; do
 	"-f")
 		force=1
 		;;
+	--)
+		break
+		;;
 	*)
-		rev=$(git-rev-parse --verify "$arg^0" 2>/dev/null) ||
-			die "I don't know any '$arg'."
-		if [ -z "$rev" ]; then
-			echo "unknown flag $arg"
-			exit 1
-		fi
-		if [ "$new" ]; then
-			echo "Multiple revisions?"
-			exit 1
-		fi
-		new="$rev"
-		if [ -f "$GIT_DIR/refs/heads/$arg" ]; then
-			branch="$arg"
+		if rev=$(git-rev-parse --verify "$arg^0" 2>/dev/null)
+		then
+			if [ -z "$rev" ]; then
+				echo "unknown flag $arg"
+				exit 1
+			fi
+			new="$rev"
+			if [ -f "$GIT_DIR/refs/heads/$arg" ]; then
+				branch="$arg"
+			fi
+		elif rev=$(git-rev-parse --verify "$arg^{tree}" 2>/dev/null)
+		then
+			# checking out selected paths from a tree-ish.
+			new="$rev"
+			branch=
+		else
+			new=
+			branch=
+			set x "$arg" "$@"
+			shift
 		fi
+		break
 		;;
     esac
 done
-[ -z "$new" ] && new=$old
 
+# The behaviour of the command with and without explicit path
+# parameters is quite different.
+#
+# Without paths, we are checking out everything in the work tree,
+# possibly switching branches.  This is the traditional behaviour.
 #
+# With paths, we are _never_ switching branch, but checking out
+# the named paths from either index (when no rev is given),
+# or the named tree-ish (when rev is given).
+
+if test "$#" -ge 1
+then
+	if test '' != "$newbranch$force"
+	then
+		die "updating paths and switching branches or forcing are incompatible."
+	fi
+	if test '' != "$new"
+	then
+		# from a specific tree-ish; note that this is for
+		# rescuing paths and is never meant to remove what
+		# is not in the named tree-ish.
+		git-ls-tree -r "$new" "$@" |
+		sed -ne 's/^\([0-7]*\) blob \(.*\)$/\1 \2/p' |
+		git-update-index --index-info || exit $?
+	fi
+	git-checkout-index -f -u -- "$@"
+	exit $?
+else
+	# Make sure we did not fall back on $arg^{tree} codepath
+	# since we are not checking out from an arbitrary tree-ish,
+	# but switching branches.
+	if test '' != "$new"
+	then
+		git-rev-parse --verify "$new^{commit}" >/dev/null 2>&1 ||
+		die "Cannot switch branch to a non-commit."
+	fi
+fi
+
+[ -z "$new" ] && new=$old
+
 # If we don't have an old branch that we're switching to,
 # and we don't have a new branch name for the target we
 # are switching to, then we'd better just be checking out
 # what we already had
-#
+
 [ -z "$branch$newbranch" ] &&
 	[ "$new" != "$old" ] &&
 	die "git checkout: you need to specify a new branch name"