From 89284c1d6ca03480a93f9d95a2460a09390f3c40 Mon Sep 17 00:00:00 2001 From: Taylor Blau Date: Mon, 8 Oct 2018 11:09:28 -0700 Subject: [PATCH] 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 Acked-by: Jeff King Signed-off-by: Junio C Hamano --- Documentation/config.txt | 11 ++++++++++ t/t5410-receive-pack-alternates.sh | 33 ++++++++++++++++++++++++++++++ transport.c | 19 +++++++++++++---- 3 files changed, 59 insertions(+), 4 deletions(-) create mode 100755 t/t5410-receive-pack-alternates.sh diff --git a/Documentation/config.txt b/Documentation/config.txt index eb66a11975..00224dea61 100644 --- a/Documentation/config.txt +++ b/Documentation/config.txt @@ -616,6 +616,17 @@ core.preferSymlinkRefs:: This is sometimes needed to work with old scripts that expect HEAD to be a symbolic link. +core.alternateRefsCommand:: + When advertising tips of available history from an alternate, use the shell to + execute the specified command instead of linkgit:git-for-each-ref[1]. The + first argument is the absolute path of the alternate. Output must contain one + hex object id per line (i.e., the same as produce by `git for-each-ref + --format='%(objectname)'`). ++ +Note that you cannot generally put `git for-each-ref` directly into the config +value, as it does not take a repository path as an argument (but you can wrap +the command above in a shell script). + core.bare:: If true this repository is assumed to be 'bare' and has no working directory associated with it. If this is the case a diff --git a/t/t5410-receive-pack-alternates.sh b/t/t5410-receive-pack-alternates.sh new file mode 100755 index 0000000000..49d0fe44fb --- /dev/null +++ b/t/t5410-receive-pack-alternates.sh @@ -0,0 +1,33 @@ +#!/bin/sh + +test_description='git receive-pack with alternate ref filtering' + +. ./test-lib.sh + +test_expect_success 'setup' ' + test_commit base && + git clone -s --bare . fork && + git checkout -b public/branch master && + test_commit public && + git checkout -b private/branch master && + test_commit private +' + +extract_haves () { + depacketize | perl -lne '/^(\S+) \.have/ and print $1' +} + +test_expect_success 'with core.alternateRefsCommand' ' + write_script fork/alternate-refs <<-\EOF && + git --git-dir="$1" for-each-ref \ + --format="%(objectname)" \ + refs/heads/public/ + EOF + test_config -C fork core.alternateRefsCommand alternate-refs && + git rev-parse public/branch >expect && + printf "0000" | git receive-pack fork >actual && + extract_haves actual.haves && + test_cmp expect actual.haves +' + +test_done diff --git a/transport.c b/transport.c index 25d8ea7fe5..19baec7942 100644 --- a/transport.c +++ b/transport.c @@ -1328,10 +1328,21 @@ literal_copy: static void fill_alternate_refs_command(struct child_process *cmd, const char *repo_path) { - cmd->git_cmd = 1; - argv_array_pushf(&cmd->args, "--git-dir=%s", repo_path); - argv_array_push(&cmd->args, "for-each-ref"); - argv_array_push(&cmd->args, "--format=%(objectname)"); + const char *value; + + if (!git_config_get_value("core.alternateRefsCommand", &value)) { + cmd->use_shell = 1; + + argv_array_push(&cmd->args, value); + argv_array_push(&cmd->args, repo_path); + } else { + cmd->git_cmd = 1; + + argv_array_pushf(&cmd->args, "--git-dir=%s", repo_path); + argv_array_push(&cmd->args, "for-each-ref"); + argv_array_push(&cmd->args, "--format=%(objectname)"); + } + cmd->env = local_repo_env; cmd->out = -1; } -- 2.43.2