lint: don't fail workflow on indent fail

There are multiple cases where good human readable code block is
converted to an unreadable mess by clang-format, so we don't want to
rely on clang-format completely. Also there is no way, as far as I can
see, to make clang-format only fix what we want it to fix without
breaking something.

So let's just display hints inline where clang-format is unhappy. When
reviewer sees such a warning it's a good sign that something is broken
in coding-style around this warning.

We add special script which parses diff generated by indent and
generates warning for each hunk.

Signed-off-by: Pavel Tikhomirov <ptikhomirov@virtuozzo.com>

scripts/github-indent-warnings.py

@@ -0,0 +1,33 @@
+#!/usr/bin/python3
+import sys
+import re
+
+re_file = r'^diff --git a/(\S\S*)\s.*$'
+re_line = r'^@@ -(\d\d*)\D.*@@.*$'
+
+if __name__ == '__main__':
+    if len(sys.argv) != 1 and len(sys.argv) != 2:
+        print(f'usage: {sys.argv[0]} <path/to/file>')
+        print(f'usage: <command> | {sys.argv[0]}')
+        exit(1)
+
+    input_file = sys.stdin.fileno()
+    if len(sys.argv) == 2:
+        input_file = sys.argv[1]
+
+    with open(input_file, 'r') as fi:
+        file_name = None
+        line_number = None
+        for line in fi:
+            file_matches = re.findall(re_file, line)
+            if len(file_matches) == 1:
+                file_name = file_matches[0]
+                continue
+
+            if file_name is None:
+                continue
+
+            line_matches = re.findall(re_line, line)
+            if len(line_matches) == 1:
+                line_number = int(line_matches[0]) + 3
+                print(f'::warning file={file_name},line={line_number}::clang-format: Possible coding style problem (https://github.com/checkpoint-restore/criu/blob/criu-dev/CONTRIBUTING.md#automatic-tools-to-fix-coding-style)')