scripts: gen_config.py: allow only use of Git hashes for feed revisions in profiles

In the current setup, YAML profiles for feed revision references can
only use weak Git tag-based references, like so in profiles/prpl.yml:

```yaml
 - name: feed_amx
   uri: https://gitlab.com/prpl-foundation/prplos/feeds/feed_amx.git
   revision: v11.9.0

 - name: feed_gmap
   uri: https://gitlab.com/prpl-foundation/prplos/feeds/feed_gmap.git
   revision: v1.7.2
```

Git tags can be mutable, meaning they can be changed or moved. This
introduces a risk where the reproducibility of builds cannot be
guaranteed. Therefore, relying solely on Git tags for referencing
revisions is not ideal.

To enhance the reproducibility and reliability of the builds, the feed
Git revision should support either of the following:

 1. Full Git SHA-1 hash of the Git object (a 40-character string).
 2. Human-readable reference like a Git tag, followed by an @ separator
    and then full (40-character) Git SHA

Examples of the currently only valid feed revisions:

```yaml
- name: feed_gmap
  uri: <https://gitlab.com/prpl-foundation/prplos/feeds/feed_gmap.git>
  revision: 178c8c0dea56bfe6e5f3d0af84be4b0156041291

- name: feed_gmap
  uri: <https://gitlab.com/prpl-foundation/prplos/feeds/feed_gmap.git>
  revision: v1.7.2@178c8c0dea56bfe6e5f3d0af84be4b0156041291
```

Closes: PCF-1388
Signed-off-by: Petr Štetiar <petr.stetiar@prplfoundation.org>

scripts/gen_config.py

@@ -4,6 +4,7 @@ import yaml
 from pathlib import Path
 from shutil import rmtree
 import io
+import re
 import sys
 from subprocess import run
 from os import getenv
@@ -18,12 +19,10 @@ def run_cmd(cmd: list):
     return run(cmd)
 
 
-def die(msg: str):
-    """Quit script with error message
-
-    msg (str): Error message to print
-    """
-    print(msg)
+def die(*messages: str) -> None:
+    """Prints each message on a new line and exits the program."""
+    for message in messages:
+        print(message)
     quit(1)
 
 
@@ -76,6 +75,49 @@ def load_yaml(fname: str, profile: dict):
     return profile
 
 
+def extract_sha1_from_revision(revision: str) -> str:
+    """
+    Validates the given revision string and extracts the SHA-1 hash.
+
+    A valid revision can be:
+
+     1. A full 40-character Git SHA-1 hash.
+     2. A human readable reference like Git tag followed by '@' and a full 40-character Git SHA-1 hash.
+
+    :param revision: The revision string to validate and extract the SHA-1 hash from.
+    :return: The extracted SHA-1 hash if valid, otherwise None.
+    """
+
+    full_sha1_pattern = r"^[a-f0-9]{40}$"
+    tag_full_sha1_pattern = r"^[^@]+@([a-f0-9]{40})$"
+
+    if re.match(full_sha1_pattern, revision):
+        return revision
+    elif re.match(tag_full_sha1_pattern, revision):
+        return re.match(tag_full_sha1_pattern, revision).group(1)
+    else:
+        return None
+
+
+def handle_feed_revision(profile_feed: dict, feeds: list):
+    revision = profile_feed.get("revision")
+    if not revision:
+        die(f"Please specify `revision` for the following feed: {profile_feed}")
+
+    sha1 = extract_sha1_from_revision(revision)
+    if not sha1:
+        die(
+            f"Invalid feed revision {revision} in {profile_feed} feed, valid `revision` is:",
+            " 1. A full 40-character Git SHA-1 hash.",
+            " 2. A human readable reference like Git tag followed by '@' and a full 40-character Git SHA-1 hash.",
+        )
+
+    f = profile_feed
+    feeds.append(
+        f'{f.get("method", "src-git")},{f["name"]},{f["uri"]}^{sha1}'
+    )
+
+
 if "list" in sys.argv:
     print(f"Profiles in {profile_folder}")
 
@@ -133,14 +175,11 @@ with open("feeds.conf.default", "r") as default_feeds:
 
 for p in profile.get("feeds", []):
     try:
-        f = profile["feeds"].get(p)
-        if not "revision" in f:
-            die(f"Please specify revision for the following feed: {f}")
-        feeds.append(
-            f'{f.get("method", "src-git")},{f["name"]},{f["uri"]}^{f.get("revision")}'
-        )
+        profile_feeds = profile["feeds"].get(p)
+        handle_feed_revision(profile_feeds, feeds)
     except:
-        print(f"Badly configured feed: {f}")
+        print(f"Badly configured feed: {profile_feeds}")
+        quit(1)
 
 if run_cmd(["./scripts/feeds", "setup", *feeds]).returncode:
     die(f"Error setting up feeds")