[PATCH 0/5] backfill: accept revision arguments

["Derrick Stolee via GitGitGadget" <gitgitgadget@gmail.com>]

The git backfill command assists in downloading missing blobs for blobless
partial clones. However, its current version lacks some valuable
functionality. It currently:

 1. Only walks commits reachable from HEAD.
 2. It walks all reachable commits to the full history.
 3. It can focus on the current sparse-checkout definition, but otherwise it
    doesn't focus on a given pathspec.

All of these are being updated by this patch series, which allows rev-list
options to impact the path-walk. These include:

 1. Specifying a given refspec, including --all.
 2. Modifying the commit walk, including --first-parent, commit ranges, or
    recency using --since.
 3. Modifying the set of paths to download using pathspecs.

One particularly valuable situation here is that now a user can run git
backfill -- <path> to download all versions of a specific file or a specific
directory, accelerating history queries within that path without downloading
more than necessary. This can accelerate git blame or git log -L for these
paths, where normally those commands download missing blobs one-by-one
during its diff algorithms.

This patch series is organized in the following way:

 1. A missing #include is added to prevent future compilation issues.
 2. The test repo in t5620 is expanded to make later tests more interesting.
 3. The backfill builtin parses the rev-list arguments. We test the top
    arguments that work as expected, though the pathspec arguments need
    extra work.
 4. Update the path-walk logic to work efficiently with some pathspecs, such
    as fixed prefix pathspecs, accelerating the computation.
 5. For more complicated pathspecs, do a post-filter in builtin/backfill.c
    instead of restricting the walk in the path-walk API.

The main goal of this series is to make such customizations possible, and to
improve performance where common use cases are expected. I'm open to
feedback as to whether we should consider more detailed performance analysis
or whether we should wait for how users interact with these new options
before overoptimizing unlikely use cases.

Thanks, -Stolee

Derrick Stolee (5):
  revision: include object-name.h
  t5620: prepare branched repo for revision tests
  backfill: accept revision arguments
  backfill: work with prefix pathspecs
  path-walk: support wildcard pathspecs for blob filtering

 Documentation/git-backfill.adoc |   3 +
 builtin/backfill.c              |  19 ++-
 path-walk.c                     |  61 ++++++++++
 revision.h                      |   1 +
 t/t5620-backfill.sh             | 203 +++++++++++++++++++++++++++++++-
 5 files changed, 279 insertions(+), 8 deletions(-)


base-commit: 67ad42147a7acc2af6074753ebd03d904476118f
Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-2070%2Fderrickstolee%2Fbackfill-revs-v1
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-2070/derrickstolee/backfill-revs-v1
Pull-Request: https://github.com/gitgitgadget/git/pull/2070
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