go source for verification 2026-05-22

lib/hg/goreposum.py

@@ -0,0 +1,64 @@
+# Copyright 2025 The Go Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style
+# license that can be found in the LICENSE file.
+
+# Mercurial extension to add a 'goreposum' command that
+# computes a hash of a remote repo's tag state.
+# Tag definitions can come from the .hgtags file stored in
+# any head of any branch, and the server protocol does not
+# expose the tags directly. However, the protocol does expose
+# the hashes of all the branch heads, so we can use a hash of
+# all those branch names and heads as a conservative snapshot
+# of the entire remote repo state, and use that as the tag sum.
+# Any change on the server then invalidates the tag sum,
+# even if it didn't have anything to do with tags, but at least
+# we will avoid re-cloning a server when there have been no
+# changes at all.
+#
+# Separately, this extension also adds a 'golookup' command that
+# returns the hash of a specific reference, like 'default' or a tag.
+# And golookup of a hash confirms that it still exists on the server.
+# We can use that to revalidate that specific versions still exist and
+# have the same meaning they did the last time we checked.
+#
+# Usage:
+#
+#	hg --config "extensions.goreposum=$GOROOT/lib/hg/goreposum.py" goreposum REPOURL
+
+import base64, hashlib, sys
+from mercurial import registrar, ui, hg, node
+from mercurial.i18n import _
+cmdtable = {}
+command = registrar.command(cmdtable)
+@command(b'goreposum', [], _('url'), norepo=True)
+def goreposum(ui, url):
+  """
+  goreposum computes a checksum of all the named state in the remote repo.
+  It hashes together all the branch names and hashes
+  and then all the bookmark names and hashes.
+  Tags are stored in .hgtags files in any of the branches,
+  so the branch metadata includes the tags as well.
+  """
+  h = hashlib.sha256()
+  peer = hg.peer(ui, {}, url)
+  for name, revs in peer.branchmap().items():
+    h.update(name)
+    for r in revs:
+      h.update(b' ')
+      h.update(r)
+    h.update(b'\n')
+  if (b'bookmarks' in peer.listkeys(b'namespaces')):
+    for name, rev in peer.listkeys(b'bookmarks').items():
+      h.update(name)
+      h.update(b'=')
+      h.update(rev)
+      h.update(b'\n')
+  print('r1:'+base64.standard_b64encode(h.digest()).decode('utf-8'))
+
+@command(b'golookup', [], _('url rev'), norepo=True)
+def golookup(ui, url, rev):
+  """
+  golookup looks up a single identifier in the repo,
+  printing its hash.
+  """
+  print(node.hex(hg.peer(ui, {}, url).lookup(rev)).decode('utf-8'))