scripts: allow marking commits with "Ignore-Backport:" in "find-backports" script

"find-backports" searches commit messages of upstream branches for
"Fixes:" comments. Those will then be highlighted to be backported,
if the script determines that to be necessary.

"find-backports" also honors the "cherry picked from" comments, to detect when
a patch was already backported. That is thus a way to suppress reporting a
commit to be backported.

Add another way to flag commits so they don't need backporting. Via
"Ignore-Backport:" tag.

As "find-backports" also honors "refs/notes/bugs" notes, this can be used
like:

    git notes \
      --ref refs/notes/bugs \
      append \
      -m "Ignore-Backport: e""29f00fa0c69 ('NEWS: fix entry that is targeted for 1.30 instead of 1.28')" \
      2''3364aa8f3bd6b11e2ac9e30117eaabfe1f3a9f2

1 files changed, 13 insertions, 11 deletions

diff --git a/contrib/scripts/find-backports b/contrib/scripts/find-backports
index 6cb62dcea6..7f1b8ab8dd 100755
--- a/contrib/scripts/find-backports
+++ b/contrib/scripts/find-backports
@@ -151,7 +151,7 @@ def git_ref_commit_body(ref):
 def git_ref_commit_body_get_fixes(ref):
     body = git_ref_commit_body(ref)
     result = []
-    for mo in re.finditer(re_bin("[fF]ixes: *([0-9a-z]+).*"), body):
+    for mo in re.finditer(re_bin("\\b[fF]ixes: *([0-9a-z]+)\\b"), body):
         c = mo.group(1).decode("ascii")
         h = git_ref_exists(c)
         if h:
@@ -166,16 +166,18 @@ def git_ref_commit_body_get_cherry_picked_one(ref):
         return None
     body = git_ref_commit_body(ref)
     result = None
-    for mo in re.finditer(
-        re_bin(".*\(cherry picked from commit ([0-9a-z]+)\).*"), body
-    ):
-        c = mo.group(1).decode("ascii")
-        h = git_ref_exists(c)
-        if h:
-            if not result:
-                result = [h]
-            else:
-                result.append(h)
+    for r in [
+        re_bin("\(cherry picked from commit ([0-9a-z]+)\)"),
+        re_bin("\\bIgnore-Backport: *([0-9a-z]+)\\b"),
+    ]:
+        for mo in re.finditer(r, body):
+            c = mo.group(1).decode("ascii")
+            h = git_ref_exists(c)
+            if h:
+                if not result:
+                    result = [h]
+                else:
+                    result.append(h)
     return result