Tom Saeger rightly pointed out [1] that the prefetch task ignores custom refspecs. This can lead to downloading more data than requested, and it doesn't even help the future foreground fetches that use that custom refspec. [1] https://lore.kernel.org/git/20210401184914.qmr7jhjbhp2mt3h6@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx/ This series fixes this problem by carefully replacing the start of each refspec's destination with "refs/prefetch/". If the destination already starts with "refs/", then that is replaced. Otherwise "refs/prefetch/" is just prepended. This happens inside of git fetch when a --prefetch option is given. This allows us to maniuplate a struct refspec_item instead of a full refspec string. It also simplifies our logic in testing the prefetch task. Update in V3 ============ * The fix is almost completely rewritten as an update to 'git fetch'. See the new PATCH 2 for this update. * There was some discussion of rewriting test_subcommand, but that can be delayed until a proper solution is found to complications around softer matches. Updates in V2 ============= Thanks for the close eye on this series. I appreciate the recommendations, which I believe I have responded to them all: * Fixed typos. * Made refspec_item_format() re-entrant. Consumers must free the buffer. * Cleaned up style (quoting and tabbing). Thanks, -Stolee Derrick Stolee (3): maintenance: simplify prefetch logic fetch: add --prefetch option maintenance: use 'git fetch --prefetch' Documentation/fetch-options.txt | 5 +++ Documentation/git-maintenance.txt | 6 ++-- builtin/fetch.c | 56 +++++++++++++++++++++++++++++++ builtin/gc.c | 36 +++++--------------- t/t5582-fetch-negative-refspec.sh | 30 +++++++++++++++++ t/t7900-maintenance.sh | 14 ++++---- 6 files changed, 109 insertions(+), 38 deletions(-) base-commit: 89b43f80a514aee58b662ad606e6352e03eaeee4 Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-924%2Fderrickstolee%2Fmaintenance%2Frefspec-v3 Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-924/derrickstolee/maintenance/refspec-v3 Pull-Request: https://github.com/gitgitgadget/git/pull/924 Range-diff vs v2: 1: 5aa0cb06c3f2 = 1: 4c0e983ba56f maintenance: simplify prefetch logic 2: d58a3e042ee8 < -: ------------ test-lib: use exact match for test_subcommand 3: 96388d949b98 < -: ------------ refspec: output a refspec item 4: bf296282323a < -: ------------ test-tool: test refspec input/output -: ------------ > 2: 7f488eea6dbd fetch: add --prefetch option 5: 9592224e3d42 ! 3: ed055d772452 maintenance: allow custom refspecs during prefetch @@ Metadata Author: Derrick Stolee <dstolee@xxxxxxxxxxxxx> ## Commit message ## - maintenance: allow custom refspecs during prefetch + maintenance: use 'git fetch --prefetch' - The prefetch task previously used the default refspec source plus a - custom refspec destination to avoid colliding with remote refs: + The 'prefetch' maintenance task previously forced the following refspec + for each remote: +refs/heads/*:refs/prefetch/<remote>/* - However, some users customize their refspec to reduce how much data they - download from specific remotes. This can involve restrictive patterns - for fetching or negative patterns to avoid downloading some refs. + If a user has specified a more strict refspec for the remote, then this + prefetch task downloads more objects than necessary. - Modify fetch_remote() to iterate over the remote's refspec list and - translate that into the appropriate prefetch scenario. Specifically, - re-parse the raw form of the refspec into a new 'struct refspec' and - modify the 'dst' member to replace a leading "refs/" substring with - "refs/prefetch/", or prepend "refs/prefetch/" to 'dst' otherwise. - Negative refspecs do not have a 'dst' so they can be transferred to the - 'git fetch' command unmodified. - - This prefix change provides the benefit of keeping whatever collisions - may exist in the custom refspecs, if that is a desirable outcome. - - This changes the names of the refs that would be fetched by the default - refspec. Instead of "refs/prefetch/<remote>/<branch>" they will now go - to "refs/prefetch/remotes/<remote>/<branch>". While this is a change, it - is not a seriously breaking one: these refs are intended to be hidden - and not used. + The previous change introduced the '--prefetch' option to 'git fetch' + which manipulates the remote's refspec to place all resulting refs into + refs/prefetch/, with further partitioning based on the destinations of + those refspecs. Update the documentation to be more generic about the destination refs. - Do not mention custom refpecs explicitly, as that does not need to be + Do not mention custom refspecs explicitly, as that does not need to be highlighted in this documentation. The important part of placing refs in - refs/prefetch remains. + refs/prefetch/ remains. Reported-by: Tom Saeger <tom.saeger@xxxxxxxxxx> Signed-off-by: Derrick Stolee <dstolee@xxxxxxxxxxxxx> ## Documentation/git-maintenance.txt ## -@@ Documentation/git-maintenance.txt: prefetch:: +@@ Documentation/git-maintenance.txt: commit-graph:: + prefetch:: + The `prefetch` task updates the object directory with the latest objects from all registered remotes. For each remote, a `git fetch` - command is run. The refmap is custom to avoid updating local or remote - branches (those in `refs/heads` or `refs/remotes`). Instead, the +- command is run. The refmap is custom to avoid updating local or remote +- branches (those in `refs/heads` or `refs/remotes`). Instead, the - remote refs are stored in `refs/prefetch/<remote>/`. Also, tags are - not updated. -+ refs are stored in `refs/prefetch/`. Also, tags are not updated. ++ command is run. The configured refspec is modified to place all ++ requested refs within `refs/prefetch/`. Also, tags are not updated. + This is done to avoid disrupting the remote-tracking branches. The end users expect these refs to stay unmoved unless they initiate a fetch. With prefetch ## builtin/gc.c ## -@@ - #include "remote.h" - #include "object-store.h" - #include "exec-cmd.h" -+#include "refspec.h" - - #define FAILED_RUN "failed to run %s" - @@ builtin/gc.c: static int fetch_remote(struct remote *remote, void *cbdata) - { - struct maintenance_run_opts *opts = cbdata; struct child_process child = CHILD_PROCESS_INIT; -+ int i; child.git_cmd = 1; - strvec_pushl(&child.args, "fetch", remote->name, "--prune", "--no-tags", -@@ builtin/gc.c: static int fetch_remote(struct remote *remote, void *cbdata) +- strvec_pushl(&child.args, "fetch", remote->name, "--prune", "--no-tags", ++ strvec_pushl(&child.args, "fetch", remote->name, ++ "--prefetch", "--prune", "--no-tags", + "--no-write-fetch-head", "--recurse-submodules=no", +- "--refmap=", NULL); ++ NULL); + if (opts->quiet) strvec_push(&child.args, "--quiet"); - strvec_pushf(&child.args, "+refs/heads/*:refs/prefetch/%s/*", remote->name); -+ for (i = 0; i < remote->fetch.nr; i++) { -+ struct refspec_item replace; -+ struct refspec_item *rsi = &remote->fetch.items[i]; -+ struct strbuf new_dst = STRBUF_INIT; -+ size_t ignore_len = 0; -+ char *replace_string; -+ -+ if (rsi->negative) { -+ strvec_push(&child.args, remote->fetch.raw[i]); -+ continue; -+ } -+ -+ refspec_item_init(&replace, remote->fetch.raw[i], 1); -+ -+ /* -+ * If a refspec dst starts with "refs/" at the start, -+ * then we will replace "refs/" with "refs/prefetch/". -+ * Otherwise, we will prepend the dst string with -+ * "refs/prefetch/". -+ */ -+ if (!strncmp(replace.dst, "refs/", 5)) -+ ignore_len = 5; -+ -+ strbuf_addstr(&new_dst, "refs/prefetch/"); -+ strbuf_addstr(&new_dst, replace.dst + ignore_len); -+ free(replace.dst); -+ replace.dst = strbuf_detach(&new_dst, NULL); -+ -+ replace_string = refspec_item_format(&replace); -+ strvec_push(&child.args, replace_string); -+ free(replace_string); -+ -+ refspec_item_clear(&replace); -+ } - +- return !!run_command(&child); } + ## t/t7900-maintenance.sh ## @@ t/t7900-maintenance.sh: test_expect_success 'prefetch multiple remotes' ' + test_commit -C clone1 one && test_commit -C clone2 two && GIT_TRACE2_EVENT="$(pwd)/run-prefetch.txt" git maintenance run --task=prefetch 2>/dev/null && - fetchargs="--prune --no-tags --no-write-fetch-head --recurse-submodules=no --refmap= --quiet" && -- test_subcommand git fetch remote1 $fetchargs "+refs/heads/*:refs/prefetch/remote1/*" <run-prefetch.txt && -- test_subcommand git fetch remote2 $fetchargs "+refs/heads/*:refs/prefetch/remote2/*" <run-prefetch.txt && -+ test_subcommand git fetch remote1 $fetchargs "+refs/heads/*:refs/prefetch/remotes/remote1/*" <run-prefetch.txt && -+ test_subcommand git fetch remote2 $fetchargs "+refs/heads/*:refs/prefetch/remotes/remote2/*" <run-prefetch.txt && +- fetchargs="--prune --no-tags --no-write-fetch-head --recurse-submodules=no --refmap= --quiet" && +- test_subcommand git fetch remote1 $fetchargs +refs/heads/\\*:refs/prefetch/remote1/\\* <run-prefetch.txt && +- test_subcommand git fetch remote2 $fetchargs +refs/heads/\\*:refs/prefetch/remote2/\\* <run-prefetch.txt && ++ fetchargs="--prefetch --prune --no-tags --no-write-fetch-head --recurse-submodules=no --quiet" && ++ test_subcommand git fetch remote1 $fetchargs <run-prefetch.txt && ++ test_subcommand git fetch remote2 $fetchargs <run-prefetch.txt && test_path_is_missing .git/refs/remotes && - git log prefetch/remote1/one && - git log prefetch/remote2/two && @@ t/t7900-maintenance.sh: test_expect_success 'prefetch multiple remotes' ' test_cmp_config refs/prefetch/ log.excludedecoration && git log --oneline --decorate --all >log && - ! grep "prefetch" log - ' - -+test_expect_success 'prefetch custom refspecs' ' -+ git -C clone1 branch -f special/fetched HEAD && -+ git -C clone1 branch -f special/secret/not-fetched HEAD && -+ -+ # create multiple refspecs for remote1 -+ git config --add remote.remote1.fetch "+refs/heads/special/fetched:refs/heads/fetched" && -+ git config --add remote.remote1.fetch "^refs/heads/special/secret/not-fetched" && -+ -+ GIT_TRACE2_EVENT="$(pwd)/prefetch-refspec.txt" git maintenance run --task=prefetch 2>/dev/null && -+ -+ fetchargs="--prune --no-tags --no-write-fetch-head --recurse-submodules=no --refmap= --quiet" && -+ -+ # skips second refspec because it is not a pattern type -+ rs1="+refs/heads/*:refs/prefetch/remotes/remote1/*" && -+ rs2="+refs/heads/special/fetched:refs/prefetch/heads/fetched" && -+ rs3="^refs/heads/special/secret/not-fetched" && -+ -+ test_subcommand git fetch remote1 $fetchargs "$rs1" "$rs2" "$rs3" <prefetch-refspec.txt && -+ test_subcommand git fetch remote2 $fetchargs "+refs/heads/*:refs/prefetch/remotes/remote2/*" <prefetch-refspec.txt && -+ -+ # first refspec is overridden by second -+ test_must_fail git rev-parse refs/prefetch/special/fetched && -+ git rev-parse refs/prefetch/heads/fetched && -+ -+ # possible incorrect places for the non-fetched ref -+ test_must_fail git rev-parse refs/prefetch/remotes/remote1/secret/not-fetched && -+ test_must_fail git rev-parse refs/prefetch/remotes/remote1/not-fetched && -+ test_must_fail git rev-parse refs/heads/secret/not-fetched && -+ test_must_fail git rev-parse refs/heads/not-fetched -+' -+ - test_expect_success 'prefetch and existing log.excludeDecoration values' ' - git config --unset-all log.excludeDecoration && - git config log.excludeDecoration refs/remotes/remote1/ && -- gitgitgadget
