@matheusbsbs / matheus-bagliano / commits / 770f389b2d

refs/files: handle F/D conflicts in case-insensitive FS

When using the files-backend on case-insensitive filesystems, there is possibility of hitting F/D conflicts when creating references within a single transaction, such as: - 'refs/heads/foo' - 'refs/heads/Foo/bar' Ideally such conflicts are caught in `refs_verify_refnames_available()` which is responsible for checking F/D conflicts within a given transaction. This utility function is shared across the reference backends. As such, it doesn't consider the issues of using a case-insensitive file system, which only affects the files-backend. While one solution would be to make the function aware of such issues, this feels like leaking implementation details of file-backend specific issues into the utility function. So opt for the more simpler option, of lowercasing all references sent to this function when on a case-insensitive filesystem and operating on the files-backend. To do this, simply use a `struct strbuf` to convert the refname to lowercase and append it to the list of refnames to be checked. Since we use a `struct strbuf` and the memory is cleared right after, make sure that the string list duplicates all provided string. Without this change, the user would simply be left with a repository with '.lock' files which were created in the 'prepare' phase of the transaction, as the 'commit' phase would simply abort and not do the necessary cleanup. Reported-by: Junio C Hamano <gitster@pobox.com> Signed-off-by: Karthik Nayak <karthik.188@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>

Karthik Nayak committed Sep 17, 2025 at 17:25 UTC 770f389b2d4b7a8f22d6350bed32effa74bd2253

2 files changed +37 -2

refs/files-backend.c

+17 -2

@@ -906,8 +906,23 @@ retry:

906 * If the ref did not exist and we are creating it, we have to

907 * make sure there is no existing packed ref that conflicts

908 * with refname. This check is deferred so that we can batch it.

909 + *

910 + * For case-insensitive filesystems, we should also check for F/D

911 + * conflicts between 'foo' and 'Foo/bar'. So let's lowercase

912 + * the refname.

913 */

910 - item = string_list_append(refnames_to_check, refname);

914 + if (ignore_case) {

915 + struct strbuf lower = STRBUF_INIT;

916 +

917 + strbuf_addstr(&lower, refname);

918 + strbuf_tolower(&lower);

919 +

920 + item = string_list_append_nodup(refnames_to_check,

921 + strbuf_detach(&lower, NULL));

922 + } else {

923 + item = string_list_append(refnames_to_check, refname);

924 + }

925 +

926 item->util = xmalloc(sizeof(update_idx));

927 memcpy(item->util, &update_idx, sizeof(update_idx));

928 }

@@ -2832,7 +2847,7 @@ static int files_transaction_prepare(struct ref_store *ref_store,

2847 "ref_transaction_prepare");

2848 size_t i;

2849 int ret = 0;

2835 - struct string_list refnames_to_check = STRING_LIST_INIT_NODUP;

2850 + struct string_list refnames_to_check = STRING_LIST_INIT_DUP;

2851 char *head_ref = NULL;

2852 int head_type;

2853 struct files_transaction_backend_data *backend_data;

t/t5510-fetch.sh

+20

@@ -53,6 +53,12 @@ test_expect_success "clone and setup child repos" '

53 cd case_sensitive &&

54 git branch branch1 &&

55 git branch bRanch1

56 + ) &&

57 + git clone --ref-format=reftable . case_sensitive_fd &&

58 + (

59 + cd case_sensitive_fd &&

60 + git branch foo/bar &&

61 + git branch Foo

62 )

63 '

@@ -1572,6 +1578,20 @@ test_expect_success REFFILES 'existing reference lock in repo' '

1578 )

1579 '

1580

1581 +test_expect_success CASE_INSENSITIVE_FS,REFFILES 'F/D conflict on case insensitive filesystem' '

1582 + test_when_finished rm -rf case_insensitive &&

1583 + (

1584 + git init --bare case_insensitive &&

1585 + cd case_insensitive &&

1586 + git remote add origin -- ../case_sensitive_fd &&

1587 + test_must_fail git fetch -f origin "refs/heads/*:refs/heads/*" 2>err &&

1588 + test_grep "failed: refname conflict" err &&

1589 + git rev-parse refs/heads/main >expect &&

1590 + git rev-parse refs/heads/foo/bar >actual &&

1591 + test_cmp expect actual

1592 + )

1593 +'

1594 +

1595 . "$TEST_DIRECTORY"/lib-httpd.sh

1596 start_httpd

1597