ci: pre-commit: Fix the gst-indent hook not implementing filtering criteria

There's a different way to list the files between the former pre-commit
hook (which ran gst-indent directly on the output of git diff-index)
and the former CI check job (which ran gst-indent-all wholesale).

It can be easily addressed by detecting CI_PROJECT_NAME at listing time.

Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/8409>

.pre-commit-config.yaml

@@ -16,8 +16,9 @@ repos:
     -   id: gst-indent
         name: gst-indent
         language: python
-        entry: ./scripts/gst-indent.py
-        types_or: ["c"]
+        entry: ./scripts/gst-indent-all.py
+        pass_filenames: false
+        types_or: ["c", "c++"]
     # The rust hook uses cargo fmt, which requires a Cargo.toml
     # We use a local hook to run rustfmt directly
     -   id: rustfmt

scripts/gst-indent-all.py

@@ -0,0 +1,44 @@
+#!/usr/bin/env python
+
+from itertools import filterfalse
+import os
+import re
+import subprocess
+from gst_indent_common import indent
+
+def readfile(f):
+    if os.path.exists(f):
+        expressions = open(f, 'r', encoding='utf-8').read().splitlines()
+        expressions = [re.compile(i) for i in expressions]
+        return lambda x: any(i.match(x) for i in expressions)
+    else:
+        return None
+
+
+def listfiles(single_glob):
+    if os.environ.get("CI_PROJECT_NAME"):
+        return subprocess.check_output(['git', 'ls-files', single_glob],
+                                       universal_newlines=True).splitlines()
+    else:
+        return subprocess.check_output(['git', 'diff-index', '--cached', '--name-only', 'HEAD', '--diff-filter=ACMR', single_glob],
+                                       universal_newlines=True).splitlines()
+
+
+if __name__ == '__main__':
+    basedir = os.path.dirname(__file__)
+
+    filter_in_c = readfile('.indentignore')
+    listing = listfiles('*.c')
+    if filter_in_c:
+        listing = filterfalse(filter_in_c, listing)
+
+    for entry in listing:
+        indent(entry)
+
+    filter_in_cpp = readfile('.indent_cpp_list')
+    listing = listfiles('*.cpp')
+    if filter_in_cpp:
+        listing = filter(filter_in_cpp, listing)
+
+    for entry in listing:
+        indent(entry)