merge(3p/git): Merge git subtree at v2.29.2 r/1890

This also bumps the stable nixpkgs to 20.09 as of 2020-11-21, because
there is some breakage in the git build related to the netrc
credentials helper which someone has taken care of in nixpkgs.

The stable channel is not used for anything other than git, so this
should be fine.

Change-Id: I3575a19dab09e1e9556cf8231d717de9890484fb

1 files changed, 79 insertions, 0 deletions

diff --git a/third_party/git/Documentation/git-maintenance.txt b/third_party/git/Documentation/git-maintenance.txt
new file mode 100644
index 000000000000..6abcb8255a2b
--- /dev/null
+++ b/third_party/git/Documentation/git-maintenance.txt
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+git-maintenance(1)
+==================
+
+NAME
+----
+git-maintenance - Run tasks to optimize Git repository data
+
+
+SYNOPSIS
+--------
+[verse]
+'git maintenance' run [<options>]
+
+
+DESCRIPTION
+-----------
+Run tasks to optimize Git repository data, speeding up other Git commands
+and reducing storage requirements for the repository.
+
+Git commands that add repository data, such as `git add` or `git fetch`,
+are optimized for a responsive user experience. These commands do not take
+time to optimize the Git data, since such optimizations scale with the full
+size of the repository while these user commands each perform a relatively
+small action.
+
+The `git maintenance` command provides flexibility for how to optimize the
+Git repository.
+
+SUBCOMMANDS
+-----------
+
+run::
+	Run one or more maintenance tasks. If one or more `--task` options
+	are specified, then those tasks are run in that order. Otherwise,
+	the tasks are determined by which `maintenance.<task>.enabled`
+	config options are true. By default, only `maintenance.gc.enabled`
+	is true.
+
+TASKS
+-----
+
+commit-graph::
+	The `commit-graph` job updates the `commit-graph` files incrementally,
+	then verifies that the written data is correct. The incremental
+	write is safe to run alongside concurrent Git processes since it
+	will not expire `.graph` files that were in the previous
+	`commit-graph-chain` file. They will be deleted by a later run based
+	on the expiration delay.
+
+gc::
+	Clean up unnecessary files and optimize the local repository. "GC"
+	stands for "garbage collection," but this task performs many
+	smaller tasks. This task can be expensive for large repositories,
+	as it repacks all Git objects into a single pack-file. It can also
+	be disruptive in some situations, as it deletes stale data. See
+	linkgit:git-gc[1] for more details on garbage collection in Git.
+
+OPTIONS
+-------
+--auto::
+	When combined with the `run` subcommand, run maintenance tasks
+	only if certain thresholds are met. For example, the `gc` task
+	runs when the number of loose objects exceeds the number stored
+	in the `gc.auto` config setting, or when the number of pack-files
+	exceeds the `gc.autoPackLimit` config setting.
+
+--quiet::
+	Do not report progress or other information over `stderr`.
+
+--task=<task>::
+	If this option is specified one or more times, then only run the
+	specified tasks in the specified order. If no `--task=<task>`
+	arguments are specified, then only the tasks with
+	`maintenance.<task>.enabled` configured as `true` are considered.
+	See the 'TASKS' section for the list of accepted `<task>` values.
+
+GIT
+---
+Part of the linkgit:git[1] suite