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, 26 insertions, 0 deletions

diff --git a/third_party/git/Documentation/config/feature.txt b/third_party/git/Documentation/config/feature.txt
new file mode 100644
index 000000000000..cdecd04e5bb7
--- /dev/null
+++ b/third_party/git/Documentation/config/feature.txt
@@ -0,0 +1,26 @@
+feature.*::
+	The config settings that start with `feature.` modify the defaults of
+	a group of other config settings. These groups are created by the Git
+	developer community as recommended defaults and are subject to change.
+	In particular, new config options may be added with different defaults.
+
+feature.experimental::
+	Enable config options that are new to Git, and are being considered for
+	future defaults. Config settings included here may be added or removed
+	with each release, including minor version updates. These settings may
+	have unintended interactions since they are so new. Please enable this
+	setting if you are interested in providing feedback on experimental
+	features. The new default values are:
++
+* `fetch.negotiationAlgorithm=skipping` may improve fetch negotiation times by
+skipping more commits at a time, reducing the number of round trips.
+
+feature.manyFiles::
+	Enable config options that optimize for repos with many files in the
+	working directory. With many files, commands such as `git status` and
+	`git checkout` may be slow and these new defaults improve performance:
++
+* `index.version=4` enables path-prefix compression in the index.
++
+* `core.untrackedCache=true` enables the untracked cache. This setting assumes
+that mtime is working on your machine.