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checkout: do not imply "-f" on unborn branches

When checkout sees that HEAD points to a non-existent ref, it currently acts as if "-f" was given; this behavior dates back to 5a03e7f, which enabled checkout from unborn branches in the shell version of "git-checkout". The reasoning given is to avoid the code path which tries to merge the tree contents. When checkout was converted to C, this code remained intact. The unfortunate side effect of this strategy is that the "force" code path will overwrite working tree and index state that may be precious to the user. Instead of enabling "force", this patch uses the normal "merge" codepath for an unborn branch, but substitutes the empty tree for the "old" commit. This means that in the absence of an index, any files in the working tree will be treated as untracked files, and a checkout which would overwrite them is aborted. Similarly, any paths in the index will be merged with an empty entry as the base, meaning that unless the new branch's content is identical to what's in the index, there will be a conflict and the checkout will be aborted. The user is then free to correct the situation or proceed with "-f" as appropriate. This patch also removes the "warning: you are on a branch yet to be born" message. Its function was to warn the user that we were enabling the "-f" option. Since we are no longer doing that, there is no reason for the user to care whether we are switching away from an unborn branch. Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>

Jeff King committed Aug 24, 2009 at 23:03 UTC cc580af88507ce02eca1a3a6512044dd19c84d80

2 files changed +43 -9

builtin-checkout.c

+3 -9

@@ -402,7 +402,9 @@ static int merge_working_tree(struct checkout_opts *opts,

402 topts.dir = xcalloc(1, sizeof(*topts.dir));

403 topts.dir->flags |= DIR_SHOW_IGNORED;

404 topts.dir->exclude_per_dir = ".gitignore";

405 - tree = parse_tree_indirect(old->commit->object.sha1);

405 + tree = parse_tree_indirect(old->commit ?

406 + old->commit->object.sha1 :

407 + (unsigned char *)EMPTY_TREE_SHA1_BIN);

408 init_tree_desc(&trees[0], tree->buffer, tree->size);

409 tree = parse_tree_indirect(new->commit->object.sha1);

410 init_tree_desc(&trees[1], tree->buffer, tree->size);

@@ -541,14 +543,6 @@ static int switch_branches(struct checkout_opts *opts, struct branch_info *new)

543 parse_commit(new->commit);

544 }

545

544 - if (!old.commit && !opts->force) {

545 - if (!opts->quiet) {

546 - warning("You appear to be on a branch yet to be born.");

547 - warning("Forcing checkout of %s.", new->name);

548 - }

549 - opts->force = 1;

550 - }

551 -

546 ret = merge_working_tree(opts, &old, new);

547 if (ret)

548 return ret;

t/t2015-checkout-unborn.sh new

+40

@@ -0,0 +1,40 @@

1 +#!/bin/sh

2 +

3 +test_description='checkout from unborn branch protects contents'

4 +. ./test-lib.sh

5 +

6 +test_expect_success 'setup' '

7 + mkdir parent &&

8 + (cd parent &&

9 + git init &&

10 + echo content >file &&

11 + git add file &&

12 + git commit -m base

13 + ) &&

14 + git fetch parent master:origin

15 +'

16 +

17 +test_expect_success 'checkout from unborn preserves untracked files' '

18 + echo precious >expect &&

19 + echo precious >file &&

20 + test_must_fail git checkout -b new origin &&

21 + test_cmp expect file

22 +'

23 +

24 +test_expect_success 'checkout from unborn preserves index contents' '

25 + echo precious >expect &&

26 + echo precious >file &&

27 + git add file &&

28 + test_must_fail git checkout -b new origin &&

29 + test_cmp expect file &&

30 + git show :file >file &&

31 + test_cmp expect file

32 +'

33 +

34 +test_expect_success 'checkout from unborn merges identical index contents' '

35 + echo content >file &&

36 + git add file &&

37 + git checkout -b new origin

38 +'

39 +

40 +test_done