1 files changed, 69 insertions, 31 deletions

diff --git a/git-checkout.sh b/git-checkout.sh
index 92ec069a3a..14835a4aa9 100755
--- a/git-checkout.sh
+++ b/git-checkout.sh
@@ -1,11 +1,13 @@
 #!/bin/sh
 
-USAGE='[-f] [-b <new_branch>] [-m] [<branch>] [<paths>...]'
+USAGE='[-q] [-f] [-b <new_branch>] [-m] [<branch>] [<paths>...]'
 SUBDIRECTORY_OK=Sometimes
 . git-sh-setup
+require_work_tree
 
 old_name=HEAD
 old=$(git-rev-parse --verify $old_name 2>/dev/null)
+oldbranch=$(git-symbolic-ref $old_name 2>/dev/null)
 new=
 new_name=
 force=
@@ -13,6 +15,9 @@ branch=
 newbranch=
 newbranch_log=
 merge=
+quiet=
+LF='
+'
 while [ "$#" != "0" ]; do
     arg="$1"
     shift
@@ -36,6 +41,9 @@ while [ "$#" != "0" ]; do
 	-m)
 		merge=1
 		;;
+	"-q")
+		quiet=1
+		;;
 	--)
 		break
 		;;
@@ -50,7 +58,7 @@ while [ "$#" != "0" ]; do
 				exit 1
 			fi
 			new="$rev"
-			new_name="$arg^0"
+			new_name="$arg"
 			if git-show-ref --verify --quiet -- "refs/heads/$arg"
 			then
 				branch="$arg"
@@ -131,31 +139,43 @@ fi
 
 # We are switching branches and checking out trees, so
 # we *NEED* to be at the toplevel.
-cdup=$(git-rev-parse --show-cdup)
-if test ! -z "$cdup"
-then
-	cd "$cdup"
-fi
+cd_to_toplevel
 
 [ -z "$new" ] && new=$old && new_name="$old_name"
 
-# If we don't have an old branch that we're switching to,
+# If we don't have an existing 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
+# are switching to, then we are detaching our HEAD from any
+# branch.  However, if "git checkout HEAD" detaches the HEAD
+# from the current branch, even though that may be logically
+# correct, it feels somewhat funny.  More importantly, we do not
+# want "git checkout" nor "git checkout -f" to detach HEAD.
 
-[ -z "$branch$newbranch" ] &&
-	[ "$new" != "$old" ] &&
-	die "git checkout: provided reference cannot be checked out directly
+detached=
+detach_warn=
 
-  You need -b to associate a new branch with the wanted checkout. Example:
-  git checkout -b <new_branch_name> $arg
-"
+if test -z "$branch$newbranch" && test "$new" != "$old"
+then
+	detached="$new"
+	if test -n "$oldbranch" && test -z "$quiet"
+	then
+		detach_warn="Note: moving to \"$new_name\" which isn't a local branch
+If you want to create a new branch from this checkout, you may do so
+(now or later) by using -b with the checkout command again. Example:
+  git checkout -b <new_branch_name>"
+	fi
+elif test -z "$oldbranch" && test -z "$quiet"
+then
+	echo >&2 "Previous HEAD position was $old"
+fi
 
 if [ "X$old" = X ]
 then
-	echo "warning: You do not appear to currently be on a branch." >&2
-	echo "warning: Forcing checkout of $new_name." >&2
+	if test -z "$quiet"
+	then
+		echo >&2 "warning: You appear to be on a branch yet to be born."
+		echo >&2 "warning: Forcing checkout of $new_name."
+	fi
 	force=1
 fi
 
@@ -174,16 +194,12 @@ else
 	# Match the index to the working tree, and do a three-way.
     	git diff-files --name-only | git update-index --remove --stdin &&
 	work=`git write-tree` &&
-	git read-tree --reset -u $new &&
-	git read-tree -m -u --aggressive --exclude-per-directory=.gitignore $old $new $work ||
-	exit
+	git read-tree --reset -u $new || exit
 
-	if result=`git write-tree 2>/dev/null`
-	then
-	    echo >&2 "Trivially automerged."
-	else
-	    git merge-index -o git-merge-one-file -a
-	fi
+	eval GITHEAD_$new=${new_name:-${branch:-$new}} &&
+	eval GITHEAD_$work=local &&
+	export GITHEAD_$new GITHEAD_$work &&
+	git merge-recursive $old -- $new $work
 
 	# Do not register the cleanly merged paths in the index yet.
 	# this is not a real merge before committing, but just carrying
@@ -204,9 +220,9 @@ else
 	exit 0
     )
     saved_err=$?
-    if test "$saved_err" = 0
+    if test "$saved_err" = 0 && test -z "$quiet"
     then
-	test "$new" = "$old" || git diff-index --name-status "$new"
+	git diff-index --name-status "$new"
     fi
     (exit $saved_err)
 fi
@@ -226,8 +242,30 @@ if [ "$?" -eq 0 ]; then
 		git-update-ref -m "checkout: Created from $new_name" "refs/heads/$newbranch" $new || exit
 		branch="$newbranch"
 	fi
-	[ "$branch" ] &&
-	GIT_DIR="$GIT_DIR" git-symbolic-ref HEAD "refs/heads/$branch"
+	if test -n "$branch"
+	then
+		GIT_DIR="$GIT_DIR" git-symbolic-ref -m "checkout: moving to $branch" HEAD "refs/heads/$branch"
+		if test -z "$quiet"
+		then
+			echo >&2 "Switched to${newbranch:+ a new} branch \"$branch\""
+		fi
+	elif test -n "$detached"
+	then
+		# NEEDSWORK: we would want a command to detach the HEAD
+		# atomically, instead of this handcrafted command sequence.
+		# Perhaps:
+		#	git update-ref --detach HEAD $new
+		# or something like that...
+		#
+		git-rev-parse HEAD >"$GIT_DIR/HEAD.new" &&
+		mv "$GIT_DIR/HEAD.new" "$GIT_DIR/HEAD" &&
+		git-update-ref -m "checkout: moving to $arg" HEAD "$detached" ||
+			die "Cannot detach HEAD"
+		if test -n "$detach_warn"
+		then
+			echo >&2 "$detach_warn"
+		fi
+	fi
 	rm -f "$GIT_DIR/MERGE_HEAD"
 else
 	exit 1