Merge bitcoin#26589: test: small fixups/improvements for get_previous_releases.py

9b5feb7 script: small fixups/improvements for get_previous_releases.py (Sebastian Falbesoner)

Pull request description:

  This is a small follow-up to bitcoin#25650 (commit 614d468) with three fixes/improvements:

  - fix "Checksum did not match" detection, which was not adapted to the new `SHA256_SUMS` structure and hence never executed (the list of tarball names isn't directly in the dictionary's values anymore, but has to be extracted from the `'tarball'` field of each value)
  - make both help text and default tag download order deterministic by sorting default tags
  - `--tags` argument help text: add missing space between "for" and "backwards"

ACKs for top commit:
  Sjors:
    tACK 9b5feb7. Tested that if I change a checksum, or remove a release, it catches that.
  josibake:
    tested ACK bitcoin@9b5feb7

Tree-SHA512: 791fa693477eebbda7fd41f3f5ec78fe7eab57df06979aa907ab258a6945534bdc3b931ddfce0fb440c9666b98c88ce5e1b6dc353ed39e129e87d3634855165c

Author: MarcoFalke

test/get_previous_releases.py

@@ -168,7 +168,7 @@ def download_binary(tag, args) -> int:
     tarballHash = hasher.hexdigest()
 
     if tarballHash not in SHA256_SUMS or SHA256_SUMS[tarballHash]['tarball'] != tarball:
-        if tarball in SHA256_SUMS.values():
+        if tarball in [v['tarball'] for v in SHA256_SUMS.values()]:
             print("Checksum did not match")
             return 1
 
@@ -320,9 +320,8 @@ def main(args) -> int:
                         help='download release binary.')
     parser.add_argument('-t', '--target-dir', action='store',
                         help='target directory.', default='releases')
-    parser.add_argument('tags', nargs='*', default=set(
-                            [v['tag'] for v in SHA256_SUMS.values()]
-                        ),
+    all_tags = sorted([*set([v['tag'] for v in SHA256_SUMS.values()])])
+    parser.add_argument('tags', nargs='*', default=all_tags,
                         help='release tags. e.g.: v19.1.0 v19.0.0-rc.9'
                         '(if not specified, the full list needed for'
                         'backwards compatibility tests will be used)'