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The existing implementation of 'git backfill' only includes downloading missing blobs reachable from HEAD. Advanced uses may desire more general commit limiting options, such as '--all' for all references, specifying a commit range via negative references, or specifying a recency of use such as with '--since=<date>'. All of these options are available if we use setup_revisions() to parse the unknown arguments with the revision machinery. This opens up a large number of possibilities, only a small set of which are tested here. For documentation, we avoid duplicating the option documentation and instead link to the documentation of 'git rev-list'. Note that these arguments currently allow specifying a pathspec, which modifies the commit history checks but does not limit the paths used in the backfill logic. This will be updated in a future change. Signed-off-by: Derrick Stolee <stolee@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
76 lines
2.6 KiB
Plaintext
76 lines
2.6 KiB
Plaintext
git-backfill(1)
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===============
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NAME
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----
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git-backfill - Download missing objects in a partial clone
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SYNOPSIS
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--------
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[synopsis]
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git backfill [--min-batch-size=<n>] [--[no-]sparse]
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DESCRIPTION
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-----------
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Blobless partial clones are created using `git clone --filter=blob:none`
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and then configure the local repository such that the Git client avoids
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downloading blob objects unless they are required for a local operation.
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This initially means that the clone and later fetches download reachable
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commits and trees but no blobs. Later operations that change the `HEAD`
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pointer, such as `git checkout` or `git merge`, may need to download
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missing blobs in order to complete their operation.
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In the worst cases, commands that compute blob diffs, such as `git blame`,
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become very slow as they download the missing blobs in single-blob
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requests to satisfy the missing object as the Git command needs it. This
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leads to multiple download requests and no ability for the Git server to
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provide delta compression across those objects.
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The `git backfill` command provides a way for the user to request that
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Git downloads the missing blobs (with optional filters) such that the
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missing blobs representing historical versions of files can be downloaded
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in batches. The `backfill` command attempts to optimize the request by
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grouping blobs that appear at the same path, hopefully leading to good
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delta compression in the packfile sent by the server.
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In this way, `git backfill` provides a mechanism to break a large clone
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into smaller chunks. Starting with a blobless partial clone with `git
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clone --filter=blob:none` and then running `git backfill` in the local
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repository provides a way to download all reachable objects in several
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smaller network calls than downloading the entire repository at clone
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time.
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By default, `git backfill` downloads all blobs reachable from the `HEAD`
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commit. This set can be restricted or expanded using various options.
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THIS COMMAND IS EXPERIMENTAL. ITS BEHAVIOR MAY CHANGE IN THE FUTURE.
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OPTIONS
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-------
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`--min-batch-size=<n>`::
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Specify a minimum size for a batch of missing objects to request
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from the server. This size may be exceeded by the last set of
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blobs seen at a given path. The default minimum batch size is
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50,000.
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`--sparse`::
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`--no-sparse`::
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Only download objects if they appear at a path that matches the
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current sparse-checkout. If the sparse-checkout feature is enabled,
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then `--sparse` is assumed and can be disabled with `--no-sparse`.
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You may also specify the commit limiting options from linkgit:git-rev-list[1].
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SEE ALSO
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--------
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linkgit:git-clone[1],
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linkgit:git-rev-list[1]
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GIT
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---
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Part of the linkgit:git[1] suite
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