Bug 40009+40010: Add git_depth and git_branch options - v2

I made a few changes to !32 (closed), trying to make it a bit more simple (functionality should be the same).

I tested it with rbm/rbm tar firefox --target nightly and rbm/rbm fetch firefox --target nightly, after this change in tor-browser-build:

diff --git a/projects/firefox/config b/projects/firefox/config
index 3b38c83f..3cedd4bc 100644
--- a/projects/firefox/config
+++ b/projects/firefox/config
@@ -64,6 +64,8 @@ targets:
 
   nightly:
     git_hash: 'tor-browser-[% c("var/firefox_version") %]-[% c("var/torbrowser_branch") %]-1'
+    git_branch: 'tor-browser-[% c("var/firefox_version") %]-[% c("var/torbrowser_branch") %]-1'
+    git_depth: '1'
     tag_gpg_id: 0
     var:
       branding_directory: 'browser/branding/nightly'

And confirmed only one branch was cloned/fetched (and the size of the git_clones/firefox directory went from 6.5GB to 3.4GB).

@JeremyRand: does this new version of the patches look good to you?

Fixes #40009 (closed). Fixes #40010 (closed).