Bug 1773874: build(angle): explicitly set `git-log`'s `format`, `decorate`, and `abbrev-commit` options in `vendor_from_git` r=jgilbert

I discovered that my local Git configuration changed the output of the
`vendor_from_git` module when it was used to vendor in ANGLE source.
That's probably not something we want! Let's insulate ourselves from the
settings that at least I'm aware could be relevant here.

Differential Revision: https://phabricator.services.mozilla.com/D184173

gfx/angle/vendor_from_git.py

@@ -64,10 +64,22 @@ def record_cherry_picks(dir_in_gecko, merge_base_origin):
     )
 
     mb_info = run_checked(
-        "git", "log", "{}~1..{}".format(merge_base, merge_base), stdout=subprocess.PIPE
+        "git",
+        "log",
+        "--format=medium",
+        "--no-decorate",
+        "--no-abbrev-commit",
+        "{}~1..{}".format(merge_base, merge_base),
+        stdout=subprocess.PIPE,
     ).stdout
     cherries = run_checked(
-        "git", "log", merge_base + "..", stdout=subprocess.PIPE
+        "git",
+        "log",
+        "--format=medium",
+        "--no-decorate",
+        "--no-abbrev-commit",
+        merge_base + "..",
+        stdout=subprocess.PIPE,
     ).stdout
 
     with open(log_path, "wb") as f: