upload: Add support for setting patchset description

Bug: 308467447
Change-Id: I7abcbc98131b826120fc9ab85d5b889f90db4b0a
Reviewed-on: https://gerrit-review.googlesource.com/c/git-repo/+/355968
Tested-by: Sergiy Belozorov <sergiyb@chromium.org>
Reviewed-by: Mike Frysinger <vapier@google.com>
Commit-Queue: Sergiy Belozorov <sergiyb@chromium.org>

project.py

@@ -21,6 +21,7 @@ import random
 import re
 import shutil
 import stat
+import string
 import subprocess
 import sys
 import tarfile
@@ -266,6 +267,7 @@ class ReviewableBranch:
         dest_branch=None,
         validate_certs=True,
         push_options=None,
+        patchset_description=None,
     ):
         self.project.UploadForReview(
             branch=self.name,
@@ -281,6 +283,7 @@ class ReviewableBranch:
             dest_branch=dest_branch,
             validate_certs=validate_certs,
             push_options=push_options,
+            patchset_description=patchset_description,
         )
 
     def GetPublishedRefs(self):
@@ -1089,6 +1092,7 @@ class Project:
         dest_branch=None,
         validate_certs=True,
         push_options=None,
+        patchset_description=None,
     ):
         """Uploads the named branch for code review."""
         if branch is None:
@@ -1171,6 +1175,10 @@ class Project:
             opts += ["wip"]
         if ready:
             opts += ["ready"]
+        if patchset_description:
+            opts += [
+                f"m={self._encode_patchset_description(patchset_description)}"
+            ]
         if opts:
             ref_spec = ref_spec + "%" + ",".join(opts)
         cmd.append(ref_spec)
@@ -1183,6 +1191,30 @@ class Project:
                 R_PUB + branch.name, R_HEADS + branch.name, message=msg
             )
 
+    @staticmethod
+    def _encode_patchset_description(original):
+        """Applies percent-encoding for strings sent as patchset description.
+
+        The encoding used is based on but stricter than URL encoding (Section
+        2.1 of RFC 3986). The only non-escaped characters are alphanumerics, and
+        'SPACE' (U+0020) can be represented as 'LOW LINE' (U+005F) or
+        'PLUS SIGN' (U+002B).
+
+        For more information, see the Gerrit docs here:
+        https://gerrit-review.googlesource.com/Documentation/user-upload.html#patch_set_description
+        """
+        SAFE = {ord(x) for x in string.ascii_letters + string.digits}
+
+        def _enc(b):
+            if b in SAFE:
+                return chr(b)
+            elif b == ord(" "):
+                return "_"
+            else:
+                return f"%{b:02x}"
+
+        return "".join(_enc(x) for x in original.encode("utf-8"))
+
     def _ExtractArchive(self, tarpath, path=None):
         """Extract the given tar on its current location