From: Phillip Wood Date: Wed, 29 Jul 2020 09:17:48 GMT Subject: Re: [PATCH v2] fetch: optionally allow disabling FETCH_HEAD update Message-ID: <7c9592c0-1079-56b7-f456-6d2583053034@gmail.com> In-Reply-To: On 29/07/2020 10:12, Phillip Wood wrote: > On 28/07/2020 17:37, Junio C Hamano wrote: >> Derrick Stolee writes: >> >>> On 7/27/2020 12:13 PM, Junio C Hamano wrote: >>>> Derrick Stolee writes: >>>> >>>>> I'll rebase onto jc/no-update-fetch-head for the next version, since >>>>> that branch is based on v2.28.0-rc0, which is recent enough. >>>> >>>> I do not think it is wise to base a work on top of unfinished "you >>>> could do it this way, perhaps?" demonstration patch the original >>>> author does not have much inclination to finish, though. >>>> >>>> When I am really bored, I may go back to the topic to finish it, but >>>> I wouldn't mind if you took ownership of it at all. >>> >>> Ah. I didn't understand the status of that branch. I'll pull it in >>> to this topic. >> >> So here is with one of the two things that I found missing in the >> first iteration of the patch: documentation. >> >> The other thing that I found iffy (and still missing from this >> version) was what should be done when "git pull" is explicitly given >> the "--no-write-fetch-head" option. >> >> I think (but didn't check the recent code) that 'git pull' would >> pass only known-to-make-sense command line options to underlying >> 'git fetch', so it probably will barf with "unknown option", which >> is the best case.  We might want to make it sure with a new test in >> 5521.  On the other hand, if we get anything other than "no such >> option", we may want to think if we want to "fix" it or just leave >> it inside "if it hurts, don't do it" territory. >> >> Thanks. >> >> The patch without doc was Reviewed-by: Taylor Blau >> but this round has not been. >> >> -- >8 -- >> >> If you run fetch but record the result in remote-tracking branches, >> and either if you do nothing with the fetched refs (e.g. you are >> merely mirroring) or if you always work from the remote-tracking >> refs (e.g. you fetch and then merge origin/branchname separately), >> you can get away with having no FETCH_HEAD at all. >> >> Teach "git fetch" a command line option "--[no-]write-fetch-head" >> and "fetch.writeFetchHEAD" configuration variable.  Without either, >> the default is to write FETCH_HEAD, and the usual rule that the >> command line option defeats configured default applies. >> >> Note that under "--dry-run" mode, FETCH_HEAD is never written; >> otherwise you'd see list of objects in the file that you do not >> actually have.  Passing `--fetch-write-head` > > Typo, it should be `--write-fetch-head` > >> does not force `git >> fetch` to write the file. >> >> Also note that this option is explicitly passed when "git pull" >> internally invokes "git fetch", so that those who configured their >> "git fetch" not to write FETCH_HEAD would not be able to break the >> cooperation between these two commands.  "git pull" must see what >> "git fetch" got recorded in FETCH_HEAD to work correctly. >> >> Signed-off-by: Junio C Hamano >> --- >>   Documentation/config/fetch.txt  |  7 ++++++ >>   Documentation/fetch-options.txt | 10 +++++++++ >>   builtin/fetch.c                 | 19 +++++++++++++--- >>   builtin/pull.c                  |  3 ++- >>   t/t5510-fetch.sh                | 39 +++++++++++++++++++++++++++++++-- >>   5 files changed, 72 insertions(+), 6 deletions(-) >> >> diff --git a/Documentation/config/fetch.txt >> b/Documentation/config/fetch.txt >> index b20394038d..0aaa05e8c0 100644 >> --- a/Documentation/config/fetch.txt >> +++ b/Documentation/config/fetch.txt >> @@ -91,3 +91,10 @@ fetch.writeCommitGraph:: >>       merge and the write may take longer. Having an updated commit-graph >>       file helps performance of many Git commands, including `git >> merge-base`, >>       `git push -f`, and `git log --graph`. Defaults to false. >> + >> +fetch.writeFetchHEAD:: >> +    Setting it to false tells `git fetch` not to write the list >> +    of remote refs fetched in the `FETCH_HEAD` file directly >> +    under `$GIT_DIR`.  Can be countermanded from the command >> +    line with the `--[no-]write-fetch-head` option.  Defaults to >> +    true. >> diff --git a/Documentation/fetch-options.txt >> b/Documentation/fetch-options.txt >> index 6e2a160a47..6775e8499f 100644 >> --- a/Documentation/fetch-options.txt >> +++ b/Documentation/fetch-options.txt >> @@ -64,6 +64,16 @@ documented in linkgit:git-config[1]. >>   --dry-run:: >>       Show what would be done, without making any changes. >> +ifndef::git-pull[] >> +--[no-]write-fetch-head:: >> +    Write the list of remote refs fetched in the `FETCH_HEAD` >> +    file directly under `$GIT_DIR`.  This is the default unless >> +    the configuration variable `fetch.writeFetchHEAD` is set to >> +    false.  Passing `--no-write-fetch-head` from the command >> +    line tells Git not to write the file.  Under `--dry-run` >> +    option, the file is never written. >> +endif::git-pull[] >> + >>   -f:: >>   --force:: >>       When 'git fetch' is used with `:` refspec it may >> diff --git a/builtin/fetch.c b/builtin/fetch.c >> index 82ac4be8a5..3ccf69753f 100644 >> --- a/builtin/fetch.c >> +++ b/builtin/fetch.c >> @@ -56,6 +56,7 @@ static int prune_tags = -1; /* unspecified */ >>   #define PRUNE_TAGS_BY_DEFAULT 0 /* do we prune tags by default? */ >>   static int all, append, dry_run, force, keep, multiple, update_head_ok; >> +static int write_fetch_head = 1; >>   static int verbosity, deepen_relative, set_upstream; >>   static int progress = -1; >>   static int enable_auto_gc = 1; >> @@ -118,6 +119,10 @@ static int git_fetch_config(const char *k, const >> char *v, void *cb) >>           return 0; >>       } >> +    if (!strcmp(k, "fetch.writefetchhead")) { >> +        write_fetch_head = git_config_bool(k, v); >> +        return 0; >> +    } >>       return git_default_config(k, v, cb); >>   } >> @@ -162,6 +167,8 @@ static struct option builtin_fetch_options[] = { >>               PARSE_OPT_OPTARG, option_fetch_parse_recurse_submodules), >>       OPT_BOOL(0, "dry-run", &dry_run, >>            N_("dry run")), >> +    OPT_BOOL(0, "write-fetch-head", &write_fetch_head, >> +         N_("write fetched references to the FETCH_HEAD file")), >>       OPT_BOOL('k', "keep", &keep, N_("keep downloaded pack")), >>       OPT_BOOL('u', "update-head-ok", &update_head_ok, >>               N_("allow updating of HEAD ref")), >> @@ -893,7 +900,9 @@ static int store_updated_refs(const char *raw_url, >> const char *remote_name, >>       const char *what, *kind; >>       struct ref *rm; >>       char *url; >> -    const char *filename = dry_run ? "/dev/null" : >> git_path_fetch_head(the_repository); >> +    const char *filename = (!write_fetch_head >> +                ? "/dev/null" >> +                : git_path_fetch_head(the_repository)); > > I was suspicious of this as we haven't cleared write_fetch_head in the > --dry-run case yet but the test below seems to show that we still don't > write FETCH_HEAD if --dry-run is given. That makes we wonder what the > point of setting the filename based on the value of write_fetch_head is. Sorry ignore that. I misread the hunk header - we have in fact cleared write_fetch_head in the --dry-run case by the time we get here. > The rest looks good to me, though it might be worth having a test to > check that pull does indeed reject --no-write-fetch-head > > Best Wishes > > Phillip > >>       int want_status; >>       int summary_width = transport_summary_width(ref_map); >> @@ -1327,7 +1336,7 @@ static int do_fetch(struct transport *transport, >>       } >>       /* if not appending, truncate FETCH_HEAD */ >> -    if (!append && !dry_run) { >> +    if (!append && write_fetch_head) { >>           retcode = truncate_fetch_head(); >>           if (retcode) >>               goto cleanup; >> @@ -1594,7 +1603,7 @@ static int fetch_multiple(struct string_list >> *list, int max_children) >>       int i, result = 0; >>       struct argv_array argv = ARGV_ARRAY_INIT; >> -    if (!append && !dry_run) { >> +    if (!append && write_fetch_head) { >>           int errcode = truncate_fetch_head(); >>           if (errcode) >>               return errcode; >> @@ -1795,6 +1804,10 @@ int cmd_fetch(int argc, const char **argv, >> const char *prefix) >>       if (depth || deepen_since || deepen_not.nr) >>           deepen = 1; >> +    /* FETCH_HEAD never gets updated in --dry-run mode */ >> +    if (dry_run) >> +        write_fetch_head = 0; >> + >>       if (all) { >>           if (argc == 1) >>               die(_("fetch --all does not take a repository argument")); >> diff --git a/builtin/pull.c b/builtin/pull.c >> index 8159c5d7c9..e988d92b53 100644 >> --- a/builtin/pull.c >> +++ b/builtin/pull.c >> @@ -527,7 +527,8 @@ static int run_fetch(const char *repo, const char >> **refspecs) >>       struct argv_array args = ARGV_ARRAY_INIT; >>       int ret; >> -    argv_array_pushl(&args, "fetch", "--update-head-ok", NULL); >> +    argv_array_pushl(&args, "fetch", "--update-head-ok", >> +             "--write-fetch-head", NULL); >>       /* Shared options */ >>       argv_push_verbosity(&args); >> diff --git a/t/t5510-fetch.sh b/t/t5510-fetch.sh >> index a66dbe0bde..3052c2d8d5 100755 >> --- a/t/t5510-fetch.sh >> +++ b/t/t5510-fetch.sh >> @@ -539,13 +539,48 @@ test_expect_success 'fetch into the current >> branch with --update-head-ok' ' >>   ' >> -test_expect_success 'fetch --dry-run' ' >> - >> +test_expect_success 'fetch --dry-run does not touch FETCH_HEAD' ' >>       rm -f .git/FETCH_HEAD && >>       git fetch --dry-run . && >>       ! test -f .git/FETCH_HEAD >>   ' >> +test_expect_success '--no-write-fetch-head does not touch FETCH_HEAD' ' >> +    rm -f .git/FETCH_HEAD && >> +    git fetch --no-write-fetch-head . && >> +    ! test -f .git/FETCH_HEAD >> +' >> + >> +test_expect_success '--write-fetch-head gets defeated by --dry-run' ' >> +    rm -f .git/FETCH_HEAD && >> +    git fetch --dry-run --write-fetch-head . && >> +    ! test -f .git/FETCH_HEAD >> +' >> + >> +test_expect_success 'fetch.writeFetchHEAD and FETCH_HEAD' ' >> +    rm -f .git/FETCH_HEAD && >> +    git -c fetch.writeFetchHEAD=no fetch . && >> +    ! test -f .git/FETCH_HEAD >> +' >> + >> +test_expect_success 'fetch.writeFetchHEAD gets defeated by --dry-run' ' >> +    rm -f .git/FETCH_HEAD && >> +    git -c fetch.writeFetchHEAD=yes fetch --dry-run . && >> +    ! test -f .git/FETCH_HEAD >> +' >> + >> +test_expect_success 'fetch.writeFetchHEAD and --no-write-fetch-head' ' >> +    rm -f .git/FETCH_HEAD && >> +    git -c fetch.writeFetchHEAD=yes fetch --no-write-fetch-head . && >> +    ! test -f .git/FETCH_HEAD >> +' >> + >> +test_expect_success 'fetch.writeFetchHEAD and --write-fetch-head' ' >> +    rm -f .git/FETCH_HEAD && >> +    git -c fetch.writeFetchHEAD=no fetch --write-fetch-head . && >> +    test -f .git/FETCH_HEAD >> +' >> + >>   test_expect_success "should be able to fetch with duplicate refspecs" ' >>       mkdir dups && >>       ( >>