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[PATCH v2 08/23] checkout: fix bug with --to and relative HEAD

From
Eric Sunshine <sunshine@sunshineco.com>
Date
Jul 4, 2015, 00:17 UTC
Message-ID
<1435969052-540-9-git-send-email-sunshine@sunshineco.com>
In-Reply-To
<1435969052-540-1-git-send-email-sunshine@sunshineco.com>

Given "git checkout --to <path> HEAD~1", the new worktree's HEAD should begin life at the current branch's HEAD~1, however, it actually ends up at HEAD~2. The happens because:

    1. git-checkout resolves HEAD~1
    2. to satisfy is_git_directory, prepare_linked_worktree() creates a
       HEAD in the new worktree with the value of the resolved HEAD~1
    3. git-checkout re-invokes itself with the same arguments within the
       new worktree to populate the worktree
    4. the sub git-checkout resolves HEAD~1 relative to its own HEAD,
       which is the resolved HEAD~1 from the original invocation,
       resulting unexpectedly and incorrectly in HEAD~2 (relative to the
       original)

Fix this by unconditionally assigning the current worktree's HEAD as the value of the new worktree's HEAD.

As a side-effect, this change also eliminates a dependence within prepare_linked_checkout() upon 'struct branch_info'. The eventual plan is to relocate "git checkout --to" functionality to "git worktree add", and worktree.c won't have knowledge of 'struct branch_info', so removal of this dependency is a step toward that goal.

Signed-off-by: Eric Sunshine <sunshine@sunshineco.com>
---
 builtin/checkout.c     |  5 ++++-
 t/t2025-checkout-to.sh | 10 ++++++++++
 2 files changed, 14 insertions(+), 1 deletion(-)
diff --git a/builtin/checkout.c b/builtin/checkout.c
index 2079aa4..f5f953d 100644
--- a/builtin/checkout.c
+++ b/builtin/checkout.c
@@ -863,6 +863,7 @@ static int prepare_linked_checkout(const struct checkout_opts *opts,
 	struct stat st;
 	struct child_process cp;
 	int counter = 0, len, ret;
+	unsigned char rev[20];
 
 	if (!new->commit)
 		die(_("no branch specified"));
@@ -924,9 +925,11 @@ static int prepare_linked_checkout(const struct checkout_opts *opts,
 	 * value would do because this value will be ignored and
 	 * replaced at the next (real) checkout.
 	 */
+	if (!resolve_ref_unsafe("HEAD", 0, rev, NULL))
+		die(_("unable to resolve HEAD"));
 	strbuf_reset(&sb);
 	strbuf_addf(&sb, "%s/HEAD", sb_repo.buf);
-	write_file(sb.buf, 1, "%s\n", sha1_to_hex(new->commit->object.sha1));
+	write_file(sb.buf, 1, "%s\n", sha1_to_hex(rev));
 	strbuf_reset(&sb);
 	strbuf_addf(&sb, "%s/commondir", sb_repo.buf);
 	write_file(sb.buf, 1, "../..\n");
diff --git a/t/t2025-checkout-to.sh b/t/t2025-checkout-to.sh
index a8d9336..0fd731b 100755
--- a/t/t2025-checkout-to.sh
+++ b/t/t2025-checkout-to.sh
@@ -134,4 +134,14 @@ test_expect_success 'checkout with grafts' '
 	test_cmp expected actual
 '
 
+test_expect_success 'checkout --to from relative HEAD' '
+	test_commit a &&
+	test_commit b &&
+	test_commit c &&
+	git rev-parse HEAD~1 >expected &&
+	git checkout --to relhead HEAD~1 &&
+	git -C relhead rev-parse HEAD >actual &&
+	test_cmp expected actual
+'
+
 test_done
-- 
2.5.0.rc1.197.g417e668
Previous: Eric SunshineNext: Duy Nguyen
Message 12 of 38 in “replace "checkout --to" with "worktree add"”
  1. 00/23 replace "checkout --to" with "worktree add"Eric Sunshine, Jul 4, 2015
  2. 01/23 Documentation/git-checkout: fix incorrect worktree prune commandEric Sunshine, Jul 4, 2015
  3. 02/23 Documentation/git-worktree: associate options with commandsEric Sunshine, Jul 4, 2015
  4. 03/23 Documentation: move linked worktree description from checkout to worktreeEric Sunshine, Jul 4, 2015
  5. 04/23 Documentation/git-worktree: add BUGS sectionEric Sunshine, Jul 4, 2015
  6. Duy NguyenJul 4, 2015
  7. Eric SunshineJul 4, 2015
  8. 05/23 Documentation/git-worktree: split technical info from general descriptionEric Sunshine, Jul 4, 2015
  9. 06/23 Documentation/git-worktree: add high-level 'lock' overviewEric Sunshine, Jul 4, 2015
  10. 07/23 Documentation/git-worktree: add EXAMPLES sectionEric Sunshine, Jul 4, 2015
  11. Eric SunshineJul 4, 2015
  12. 08/23 checkout: fix bug with --to and relative HEADEric Sunshine, Jul 4, 2015
  13. Duy NguyenJul 4, 2015
  14. Eric SunshineJul 4, 2015
  15. 09/23 checkout: relocate --to's "no branch specified" checkEric Sunshine, Jul 4, 2015
  16. 10/23 checkout: prepare_linked_checkout: drop now-unused 'new' argumentEric Sunshine, Jul 4, 2015
  17. 11/23 checkout: make --to unconditionally verboseEric Sunshine, Jul 4, 2015
  18. 12/23 checkout: drop 'checkout_opts' dependency from prepare_linked_checkoutEric Sunshine, Jul 4, 2015
  19. 13/23 worktree: introduce "add" commandEric Sunshine, Jul 4, 2015
  20. Duy NguyenJul 4, 2015
  21. Eric SunshineJul 4, 2015
  22. Duy NguyenJul 6, 2015
  23. 14/23 worktree: add --force optionEric Sunshine, Jul 4, 2015
  24. 15/23 worktree: add --detach optionEric Sunshine, Jul 4, 2015
  25. 16/23 worktree: add -b/-B optionsEric Sunshine, Jul 4, 2015
  26. Duy NguyenJul 4, 2015
  27. Eric SunshineJul 4, 2015
  28. 17/23 tests: worktree: retrofit "checkout --to" tests for "worktree add"Eric Sunshine, Jul 4, 2015
  29. 18/23 checkout: retire --to optionEric Sunshine, Jul 4, 2015
  30. Duy NguyenJul 4, 2015
  31. Eric SunshineJul 4, 2015
  32. 19/23 checkout: require worktree unconditionallyEric Sunshine, Jul 4, 2015
  33. Eric SunshineJul 4, 2015
  34. 20/23 worktree: extract basename computation to new functionEric Sunshine, Jul 4, 2015
  35. 21/23 worktree: add: make -b/-B default to HEAD when <branch> is omittedEric Sunshine, Jul 4, 2015
  36. Junio C HamanoJul 6, 2015
  37. 22/23 worktree: add: auto-vivify new branch when <branch> is omittedEric Sunshine, Jul 4, 2015
  38. 23/23 checkout: retire --ignore-other-worktrees in favor of --forceEric Sunshine, Jul 4, 2015

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