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, 14 insertions, 0 deletions

diff --git a/third_party/git/git-filter-branch.sh b/third_party/git/git-filter-branch.sh
index 5c5afa2b98..fea7964617 100755
--- a/third_party/git/git-filter-branch.sh
+++ b/third_party/git/git-filter-branch.sh
@@ -83,6 +83,20 @@ set_ident () {
 	finish_ident COMMITTER
 }
 
+if test -z "$FILTER_BRANCH_SQUELCH_WARNING$GIT_TEST_DISALLOW_ABBREVIATED_OPTIONS"
+then
+	cat <<EOF
+WARNING: git-filter-branch has a glut of gotchas generating mangled history
+	 rewrites.  Hit Ctrl-C before proceeding to abort, then use an
+	 alternative filtering tool such as 'git filter-repo'
+	 (https://github.com/newren/git-filter-repo/) instead.  See the
+	 filter-branch manual page for more details; to squelch this warning,
+	 set FILTER_BRANCH_SQUELCH_WARNING=1.
+EOF
+	sleep 10
+	printf "Proceeding with filter-branch...\n\n"
+fi
+
 USAGE="[--setup <command>] [--subdirectory-filter <directory>] [--env-filter <command>]
 	[--tree-filter <command>] [--index-filter <command>]
 	[--parent-filter <command>] [--msg-filter <command>]