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

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

third_party/git/Documentation/config.txt

@@ -3,11 +3,12 @@ CONFIGURATION FILE
 
 The Git configuration file contains a number of variables that affect
 the Git commands' behavior. The files `.git/config` and optionally
-`config.worktree` (see `extensions.worktreeConfig` below) in each
-repository are used to store the configuration for that repository, and
-`$HOME/.gitconfig` is used to store a per-user configuration as
-fallback values for the `.git/config` file. The file `/etc/gitconfig`
-can be used to store a system-wide default configuration.
+`config.worktree` (see the "CONFIGURATION FILE" section of
+linkgit:git-worktree[1]) in each repository are used to store the
+configuration for that repository, and `$HOME/.gitconfig` is used to
+store a per-user configuration as fallback values for the `.git/config`
+file. The file `/etc/gitconfig` can be used to store a system-wide
+default configuration.
 
 The configuration variables are used by both the Git plumbing
 and the porcelains. The variables are divided into sections, wherein
@@ -142,7 +143,7 @@ refer to linkgit:gitignore[5] for details. For convenience:
 
 `gitdir/i`::
 	This is the same as `gitdir` except that matching is done
-	case-insensitively (e.g. on case-insensitive file sytems)
+	case-insensitively (e.g. on case-insensitive file systems)
 
 `onbranch`::
 	The data that follows the keyword `onbranch:` is taken to be a
@@ -178,52 +179,54 @@ to either specify only the realpath version, or both versions.
 Example
 ~~~~~~~
 
-	# Core variables
-	[core]
-		; Don't trust file modes
-		filemode = false
+----
+# Core variables
+[core]
+	; Don't trust file modes
+	filemode = false
 
-	# Our diff algorithm
-	[diff]
-		external = /usr/local/bin/diff-wrapper
-		renames = true
+# Our diff algorithm
+[diff]
+	external = /usr/local/bin/diff-wrapper
+	renames = true
 
-	[branch "devel"]
-		remote = origin
-		merge = refs/heads/devel
+[branch "devel"]
+	remote = origin
+	merge = refs/heads/devel
 
-	# Proxy settings
-	[core]
-		gitProxy="ssh" for "kernel.org"
-		gitProxy=default-proxy ; for the rest
+# Proxy settings
+[core]
+	gitProxy="ssh" for "kernel.org"
+	gitProxy=default-proxy ; for the rest
 
-	[include]
-		path = /path/to/foo.inc ; include by absolute path
-		path = foo.inc ; find "foo.inc" relative to the current file
-		path = ~/foo.inc ; find "foo.inc" in your `$HOME` directory
+[include]
+	path = /path/to/foo.inc ; include by absolute path
+	path = foo.inc ; find "foo.inc" relative to the current file
+	path = ~/foo.inc ; find "foo.inc" in your `$HOME` directory
 
-	; include if $GIT_DIR is /path/to/foo/.git
-	[includeIf "gitdir:/path/to/foo/.git"]
-		path = /path/to/foo.inc
+; include if $GIT_DIR is /path/to/foo/.git
+[includeIf "gitdir:/path/to/foo/.git"]
+	path = /path/to/foo.inc
 
-	; include for all repositories inside /path/to/group
-	[includeIf "gitdir:/path/to/group/"]
-		path = /path/to/foo.inc
+; include for all repositories inside /path/to/group
+[includeIf "gitdir:/path/to/group/"]
+	path = /path/to/foo.inc
 
-	; include for all repositories inside $HOME/to/group
-	[includeIf "gitdir:~/to/group/"]
-		path = /path/to/foo.inc
+; include for all repositories inside $HOME/to/group
+[includeIf "gitdir:~/to/group/"]
+	path = /path/to/foo.inc
 
-	; relative paths are always relative to the including
-	; file (if the condition is true); their location is not
-	; affected by the condition
-	[includeIf "gitdir:/path/to/group/"]
-		path = foo.inc
+; relative paths are always relative to the including
+; file (if the condition is true); their location is not
+; affected by the condition
+[includeIf "gitdir:/path/to/group/"]
+	path = foo.inc
 
-	; include only if we are in a worktree where foo-branch is
-	; currently checked out
-	[includeIf "onbranch:foo-branch"]
-		path = foo.inc
+; include only if we are in a worktree where foo-branch is
+; currently checked out
+[includeIf "onbranch:foo-branch"]
+	path = foo.inc
+----
 
 Values
 ~~~~~~
@@ -261,7 +264,9 @@ color::
 +
 The basic colors accepted are `normal`, `black`, `red`, `green`, `yellow`,
 `blue`, `magenta`, `cyan` and `white`.  The first color given is the
-foreground; the second is the background.
+foreground; the second is the background.  All the basic colors except
+`normal` have a bright variant that can be speficied by prefixing the
+color with `bright`, like `brightred`.
 +
 Colors may also be given as numbers between 0 and 255; these use ANSI
 256-color mode (but note that not all terminals may support this).  If
@@ -335,6 +340,8 @@ include::config/column.txt[]
 
 include::config/commit.txt[]
 
+include::config/commitgraph.txt[]
+
 include::config/credential.txt[]
 
 include::config/completion.txt[]
@@ -343,8 +350,12 @@ include::config/diff.txt[]
 
 include::config/difftool.txt[]
 
+include::config/extensions.txt[]
+
 include::config/fastimport.txt[]
 
+include::config/feature.txt[]
+
 include::config/fetch.txt[]
 
 include::config/format.txt[]
@@ -389,6 +400,8 @@ include::config/mailinfo.txt[]
 
 include::config/mailmap.txt[]
 
+include::config/maintenance.txt[]
+
 include::config/man.txt[]
 
 include::config/merge.txt[]
@@ -441,6 +454,8 @@ include::config/submodule.txt[]
 
 include::config/tag.txt[]
 
+include::config/tar.txt[]
+
 include::config/trace2.txt[]
 
 include::config/transfer.txt[]