git-commit-vandalism/Documentation/git-commit-graph.txt
Derrick Stolee 85102ac71b commit-graph: don't write commit-graph when disabled
The core.commitGraph config setting can be set to 'false' to prevent
parsing commits from the commit-graph file(s). This causes an issue when
trying to write with "--split" which needs to distinguish between
commits that are in the existing commit-graph layers and commits that
are not. The existing mechanism uses parse_commit() and follows by
checking if there is a 'graph_pos' that shows the commit was parsed from
the commit-graph file.

When core.commitGraph=false, we do not parse the commits from the
commit-graph and 'graph_pos' indicates that no commits are in the
existing file. The --split logic moves forward creating a new layer on
top that holds all reachable commits, then possibly merges down into
those layers, resulting in duplicate commits. The previous change makes
that merging process more robust to such a situation in case it happens
in the written commit-graph data.

The easy answer here is to avoid writing a commit-graph if reading the
commit-graph is disabled. Since the resulting commit-graph will would not
be read by subsequent Git processes. This is more natural than forcing
core.commitGraph to be true for the 'write' process.

Reported-by: Thomas Braun <thomas.braun@virtuell-zuhause.de>
Helped-by: Jeff King <peff@peff.net>
Helped-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2020-10-09 14:16:32 -07:00

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git-commit-graph(1)
===================
NAME
----
git-commit-graph - Write and verify Git commit-graph files
SYNOPSIS
--------
[verse]
'git commit-graph verify' [--object-dir <dir>] [--shallow] [--[no-]progress]
'git commit-graph write' <options> [--object-dir <dir>] [--[no-]progress]
DESCRIPTION
-----------
Manage the serialized commit-graph file.
OPTIONS
-------
--object-dir::
Use given directory for the location of packfiles and commit-graph
file. This parameter exists to specify the location of an alternate
that only has the objects directory, not a full `.git` directory. The
commit-graph file is expected to be in the `<dir>/info` directory and
the packfiles are expected to be in `<dir>/pack`. If the directory
could not be made into an absolute path, or does not match any known
object directory, `git commit-graph ...` will exit with non-zero
status.
--[no-]progress::
Turn progress on/off explicitly. If neither is specified, progress is
shown if standard error is connected to a terminal.
COMMANDS
--------
'write'::
Write a commit-graph file based on the commits found in packfiles. If
the config option `core.commitGraph` is disabled, then this command will
output a warning, then return success without writing a commit-graph file.
+
With the `--stdin-packs` option, generate the new commit graph by
walking objects only in the specified pack-indexes. (Cannot be combined
with `--stdin-commits` or `--reachable`.)
+
With the `--stdin-commits` option, generate the new commit graph by
walking commits starting at the commits specified in stdin as a list
of OIDs in hex, one OID per line. OIDs that resolve to non-commits
(either directly, or by peeling tags) are silently ignored. OIDs that
are malformed, or do not exist generate an error. (Cannot be combined
with `--stdin-packs` or `--reachable`.)
+
With the `--reachable` option, generate the new commit graph by walking
commits starting at all refs. (Cannot be combined with `--stdin-commits`
or `--stdin-packs`.)
+
With the `--append` option, include all commits that are present in the
existing commit-graph file.
+
With the `--changed-paths` option, compute and write information about the
paths changed between a commit and its first parent. This operation can
take a while on large repositories. It provides significant performance gains
for getting history of a directory or a file with `git log -- <path>`.
+
With the `--split[=<strategy>]` option, write the commit-graph as a
chain of multiple commit-graph files stored in
`<dir>/info/commit-graphs`. Commit-graph layers are merged based on the
strategy and other splitting options. The new commits not already in the
commit-graph are added in a new "tip" file. This file is merged with the
existing file if the following merge conditions are met:
+
* If `--split=no-merge` is specified, a merge is never performed, and
the remaining options are ignored. `--split=replace` overwrites the
existing chain with a new one. A bare `--split` defers to the remaining
options. (Note that merging a chain of commit graphs replaces the
existing chain with a length-1 chain where the first and only
incremental holds the entire graph).
+
* If `--size-multiple=<X>` is not specified, let `X` equal 2. If the new
tip file would have `N` commits and the previous tip has `M` commits and
`X` times `N` is greater than `M`, instead merge the two files into a
single file.
+
* If `--max-commits=<M>` is specified with `M` a positive integer, and the
new tip file would have more than `M` commits, then instead merge the new
tip with the previous tip.
+
Finally, if `--expire-time=<datetime>` is not specified, let `datetime`
be the current time. After writing the split commit-graph, delete all
unused commit-graph whose modified times are older than `datetime`.
'verify'::
Read the commit-graph file and verify its contents against the object
database. Used to check for corrupted data.
+
With the `--shallow` option, only check the tip commit-graph file in
a chain of split commit-graphs.
EXAMPLES
--------
* Write a commit-graph file for the packed commits in your local `.git`
directory.
+
------------------------------------------------
$ git commit-graph write
------------------------------------------------
* Write a commit-graph file, extending the current commit-graph file
using commits in `<pack-index>`.
+
------------------------------------------------
$ echo <pack-index> | git commit-graph write --stdin-packs
------------------------------------------------
* Write a commit-graph file containing all reachable commits.
+
------------------------------------------------
$ git show-ref -s | git commit-graph write --stdin-commits
------------------------------------------------
* Write a commit-graph file containing all commits in the current
commit-graph file along with those reachable from `HEAD`.
+
------------------------------------------------
$ git rev-parse HEAD | git commit-graph write --stdin-commits --append
------------------------------------------------
GIT
---
Part of the linkgit:git[1] suite