git stash: avoid data loss when "git stash save" kills a directory

"stash save" is about saving the local change to the working tree,
but also about restoring the state of the last commit to the working
tree.  When a local change is to turn a non-directory to a directory,
in order to restore the non-directory, everything in the directory
needs to be removed.

Which is fine when running "git stash save --include-untracked",
but without that option, untracked, newly created files in the
directory will have to be discarded, if the state you are restoring
to has a non-directory at the same path as the directory.

Introduce a safety valve to fail the operation in such case, using
the "ls-files --killed" which was designed for this exact purpose.

The "stash save" is stopped when untracked files need to be
discarded because their leading path ceased to be a directory, and
the user is required to pass --force to really have the data
removed.

Signed-off-by: Petr Baudis <pasky@ucw.cz>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/Documentation/git-stash.txt b/Documentation/git-stash.txt
index db7e803..7c8b648 100644 (file)
--- a/Documentation/git-stash.txt
+++ b/Documentation/git-stash.txt
@@ -14,7 +14,8 @@ SYNOPSIS
 'git stash' ( pop | apply ) [--index] [-q|--quiet] [<stash>]
 'git stash' branch <branchname> [<stash>]
 'git stash' [save [-p|--patch] [-k|--[no-]keep-index] [-q|--quiet]
-            [-u|--include-untracked] [-a|--all] [<message>]]
+            [-u|--include-untracked] [-a|--all] [-f|--force]
+            [<message>]]
 'git stash' clear
 'git stash' create [<message>]
 'git stash' store [-m|--message <message>] [-q|--quiet] <commit>
@@ -44,7 +45,7 @@ is also possible).
 OPTIONS
 -------
 
-save [-p|--patch] [--[no-]keep-index] [-u|--include-untracked] [-a|--all] [-q|--quiet] [<message>]::
+save [-p|--patch] [--[no-]keep-index] [-u|--include-untracked] [-a|--all] [-q|--quiet] [-f|--force] [<message>]::
 
        Save your local modifications to a new 'stash', and run `git reset
        --hard` to revert them.  The <message> part is optional and gives
@@ -71,6 +72,13 @@ linkgit:git-add[1] to learn how to operate the `--patch` mode.
 +
 The `--patch` option implies `--keep-index`.  You can use
 `--no-keep-index` to override this.
++
+In some cases, saving a stash could mean irretrievably removing some
+data - if a directory with untracked files replaces a tracked file of
+the same name, the new untracked files are not saved (except in case
+of `--include-untracked`) but the original tracked file shall be restored.
+By default, `stash save` will abort in such a case; `--force` will allow
+it to remove the untracked files.
 
 list [<options>]::
 

diff --git a/git-stash.sh b/git-stash.sh
index 1e541a2..85c9e2c 100755 (executable)
--- a/git-stash.sh
+++ b/git-stash.sh
@@ -195,6 +195,7 @@ save_stash () {
        keep_index=
        patch_mode=
        untracked=
+       force=
        while test $# != 0
        do
                case "$1" in
@@ -215,6 +216,9 @@ save_stash () {
                -u|--include-untracked)
                        untracked=untracked
                        ;;
+               -f|--force)
+                       force=t
+                       ;;
                -a|--all)
                        untracked=all
                        ;;
@@ -258,6 +262,14 @@ save_stash () {
                say "$(gettext "No local changes to save")"
                exit 0
        fi
+       if test -z "$untracked$force" &&
+          test -n "$(git ls-files --killed | head -n 1)"
+       then
+               say "$(gettext "The following untracked files would NOT be saved but need to be removed by stash save:")"
+               test -n "$GIT_QUIET" || git ls-files --killed | sed 's/^/\t/'
+               say "$(gettext "Aborting. Consider using either the --force or --include-untracked option.")" >&2
+               exit 1
+       fi
        test -f "$GIT_DIR/logs/$ref_stash" ||
                clear_stash || die "$(gettext "Cannot initialize stash")"
 

diff --git a/t/t3903-stash.sh b/t/t3903-stash.sh
index debda7a..5d22f17 100755 (executable)
--- a/t/t3903-stash.sh
+++ b/t/t3903-stash.sh
@@ -673,4 +673,22 @@ test_expect_success 'store updates stash ref and reflog' '
        grep quux bazzy
 '
 
+test_expect_success 'stash a change to turn a non-directory to a directory' '
+       git reset --hard &&
+       >testfile &&
+       git add testfile &&
+       git commit -m "add testfile as a regular file" &&
+       rm testfile &&
+       mkdir testfile &&
+       >testfile/file &&
+       test_must_fail git stash save "recover regular file" &&
+       test -f testfile/file
+'
+
+test_expect_success 'stash a change to turn a non-directory to a directory (forced)' '
+       git stash save --force "recover regular file (forced)" &&
+       ! test -f testfile/file &&
+       test -f testfile
+'
+
 test_done