@matheusbsbs / matheus-bagliano / commits / 89284c1d6c

transport.c: introduce core.alternateRefsCommand

When in a repository containing one or more alternates, Git would sometimes like to list references from those alternates. For example, 'git receive-pack' lists the "tips" pointed to by references in those alternates as special ".have" references. Listing ".have" references is designed to make pushing changes from upstream to a fork a lightweight operation, by advertising to the pusher that the fork already has the objects (via its alternate). Thus, the client can avoid sending them. However, when the alternate (upstream, in the previous example) has a pathologically large number of references, the initial advertisement is too expensive. In fact, it can dominate any such optimization where the pusher avoids sending certain objects. Introduce "core.alternateRefsCommand" in order to provide a facility to limit or filter alternate references. This can be used, for example, to filter out references the alternate does not wish to send (for space concerns, or otherwise) during the initial advertisement. Let the repository that has alternates configure this command to avoid trusting the alternate to provide us a safe command to run in the shell. To find the alternate, pass its absolute path as the first argument. Signed-off-by: Taylor Blau <me@ttaylorr.com> Acked-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>

Taylor Blau committed Oct 8, 2018 at 11:09 UTC 89284c1d6ca03480a93f9d95a2460a09390f3c40
3 files changed +59 -4
Documentation/config.txt
+11
@@ -616,6 +616,17 @@ core.preferSymlinkRefs::
616 This is sometimes needed to work with old scripts that
617 expect HEAD to be a symbolic link.
618
619 +core.alternateRefsCommand::
620 + When advertising tips of available history from an alternate, use the shell to
621 + execute the specified command instead of linkgit:git-for-each-ref[1]. The
622 + first argument is the absolute path of the alternate. Output must contain one
623 + hex object id per line (i.e., the same as produce by `git for-each-ref
624 + --format='%(objectname)'`).
625 ++
626 +Note that you cannot generally put `git for-each-ref` directly into the config
627 +value, as it does not take a repository path as an argument (but you can wrap
628 +the command above in a shell script).
629 +
630 core.bare::
631 If true this repository is assumed to be 'bare' and has no
632 working directory associated with it. If this is the case a
t/t5410-receive-pack-alternates.sh new
+33
@@ -0,0 +1,33 @@
1 +#!/bin/sh
2 +
3 +test_description='git receive-pack with alternate ref filtering'
4 +
5 +. ./test-lib.sh
6 +
7 +test_expect_success 'setup' '
8 + test_commit base &&
9 + git clone -s --bare . fork &&
10 + git checkout -b public/branch master &&
11 + test_commit public &&
12 + git checkout -b private/branch master &&
13 + test_commit private
14 +'
15 +
16 +extract_haves () {
17 + depacketize | perl -lne '/^(\S+) \.have/ and print $1'
18 +}
19 +
20 +test_expect_success 'with core.alternateRefsCommand' '
21 + write_script fork/alternate-refs <<-\EOF &&
22 + git --git-dir="$1" for-each-ref \
23 + --format="%(objectname)" \
24 + refs/heads/public/
25 + EOF
26 + test_config -C fork core.alternateRefsCommand alternate-refs &&
27 + git rev-parse public/branch >expect &&
28 + printf "0000" | git receive-pack fork >actual &&
29 + extract_haves <actual >actual.haves &&
30 + test_cmp expect actual.haves
31 +'
32 +
33 +test_done
transport.c
+15 -4
@@ -1328,10 +1328,21 @@ literal_copy:
1328 static void fill_alternate_refs_command(struct child_process *cmd,
1329 const char *repo_path)
1330 {
1331 - cmd->git_cmd = 1;
1332 - argv_array_pushf(&cmd->args, "--git-dir=%s", repo_path);
1333 - argv_array_push(&cmd->args, "for-each-ref");
1334 - argv_array_push(&cmd->args, "--format=%(objectname)");
1331 + const char *value;
1332 +
1333 + if (!git_config_get_value("core.alternateRefsCommand", &value)) {
1334 + cmd->use_shell = 1;
1335 +
1336 + argv_array_push(&cmd->args, value);
1337 + argv_array_push(&cmd->args, repo_path);
1338 + } else {
1339 + cmd->git_cmd = 1;
1340 +
1341 + argv_array_pushf(&cmd->args, "--git-dir=%s", repo_path);
1342 + argv_array_push(&cmd->args, "for-each-ref");
1343 + argv_array_push(&cmd->args, "--format=%(objectname)");
1344 + }
1345 +
1346 cmd->env = local_repo_env;
1347 cmd->out = -1;
1348 }