Replace perl code with pure shell code

diff --git a/git-checkout.sh b/git-checkout.sh
index dcf6ddbdf16c5c2c666aa01026912d9c425c55f2..8500f51ea27054d328be6e7e53c9f14d0d9c1979 100755 (executable)
--- a/git-checkout.sh
+++ b/git-checkout.sh
@@ -3,6 +3,7 @@
 USAGE='[-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)
@@ -134,11 +135,7 @@ 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"
 
@@ -150,21 +147,18 @@ fi
 # correct, it feels somewhat funny.  More importantly, we do not
 # want "git checkout" nor "git checkout -f" to detach HEAD.
 
+detached=
+detach_warn=
+
 if test -z "$branch$newbranch" && test "$new" != "$old"
 then
-       # NEEDSWORK: we would want to have a command here
-       # that allows us to detach the HEAD atomically.  Perhaps
-       # something like "git update-ref --detach HEAD $new"
-       echo "$new" >"$GIT_DIR/HEAD.new" &&
-       mv "$GIT_DIR/HEAD.new" "$GIT_DIR/HEAD" || die "Cannot detach HEAD"
-
+       detached="$new"
        if test -n "$oldbranch"
        then
-               echo >&2 "warning: you are not on ANY branch anymore.
-If you meant to create a new branch from the commit, you need -b to
-associate a new branch with the wanted checkout.  Example:
-  git checkout -b <new_branch_name> $arg
-"
+               detach_warn="warning: you are not on ANY branch anymore.
+If you meant to create a new branch from this checkout, you may still do
+so (now or later) by using -b with the checkout command again.  Example:
+  git checkout -b <new_branch_name>"
        fi
 elif test -z "$oldbranch" && test -n "$branch"
 then
@@ -206,16 +200,12 @@ 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
@@ -258,8 +248,25 @@ 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="$GIT_DIR" git-symbolic-ref HEAD "refs/heads/$branch"
+       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 $new
+               # or something like that...
+               #
+               echo "$detached" >"$GIT_DIR/HEAD.new" &&
+               mv "$GIT_DIR/HEAD.new" "$GIT_DIR/HEAD" ||
+                       die "Cannot detach HEAD"
+               if test -n "$detach_warn"
+               then
+                       echo >&2 "$detach_warn"
+               fi
+       fi
        rm -f "$GIT_DIR/MERGE_HEAD"
 else
        exit 1