utils/getdeveloperlib.py: handle file removal

If a patch only removes files, it is ignored. Meaning, that the
registered developer isn't automatically picked up when calling
get-developer.
Fix this by also checking if the line starts with ---, as a patch
removing a file has a line starting with --- with the name of the
removed file and one started with +++ /dev/null.
A set is used to store the changed files, which doesn't allow
duplicates. Therefore normal patches aren't affected by this change.

Signed-off-by: Daniel Lang <dalang@gmx.at>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
(cherry picked from commit 7bc5ea80c7)
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

utils/getdeveloperlib.py

@@ -25,7 +25,7 @@ def analyze_patch(patch):
         m = FIND_INFRA_IN_PATCH.match(line)
         if m:
             infras.add(m.group(2))
-        if not line.startswith("+++ "):
+        if not line.startswith("+++ ") and not line.startswith("--- "):
             continue
         line.strip()
         fname = line[line.find("/") + 1:].strip()