Write safe.directory items to system git config

This is necessary for more consistent behavior across multiple
distro versions. Apparently somewhere along the way, git started
looking at the current user's home directory instead of $HOME.

Related-Bug: https://bugs.launchpad.net/devstack/+bug/1968798

Change-Id: I941ef5ea90970a0901236afe81c551aaf24ac1d8

functions-common

@@ -677,8 +677,13 @@ function git_clone {
     # about how we clone and work with repos.  Mark them safe globally
     # as a work-around.
     #
+    # NOTE(danms): On bionic (and likely others) git-config may write
+    # ~stackuser/.gitconfig if not run with sudo -H. Using --system
+    # writes these changes to /etc/gitconfig which is more
+    # discoverable anyway.
+    #
     # [1] https://github.com/git/git/commit/8959555cee7ec045958f9b6dd62e541affb7e7d9
-    sudo git config --global --add safe.directory ${git_dest}
+    sudo git config --system --add safe.directory ${git_dest}
 
     # print out the results so we know what change was used in the logs
     cd $git_dest

unstack.sh

@@ -181,3 +181,8 @@ fi
 
 clean_pyc_files
 rm -Rf $DEST/async
+
+# Clean any safe.directory items we wrote into the global
+# gitconfig. We can identify the relevant ones by checking that they
+# point to somewhere in our $DEST directory.
+sudo sed -i "/directory=${DEST}/ d" /etc/gitconfig