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426ef30ecf
When we added -reuse in CL 411398, we only handled Git repos. This was partly because we were focused on Git traffic, partly because Git is the dominant module VCS, and partly because I couldn't see how to retrieve the metadata needed in other version control systems. This CL adds -reuse support for Mercurial, the second most popular VCS for modules, now that I see how to implement it. Although the Mercurial command line does not have sufficient information, the Mercurial Python API does, so we ship and invoke a Mercurial extension written in Python that can compute a hash of the remote repo without downloading it entirely, as well as resolve a remote name to a hash or check the continued existence of a hash. Then we can avoid downloading the repo at all if it hasn't changed since the last check or if the specific reference we need still resolves or exists. Fixes #75119. Change-Id: Ia47d89b15c1091c44efef9d325270fc400a412c4 Reviewed-on: https://go-review.googlesource.com/c/go/+/718382 Auto-Submit: Russ Cox <rsc@golang.org> Reviewed-by: Michael Matloob <matloob@golang.org> Reviewed-by: Michael Matloob <matloob@google.com> LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
64 lines
2.4 KiB
Python
64 lines
2.4 KiB
Python
# Copyright 2025 The Go Authors. All rights reserved.
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# Use of this source code is governed by a BSD-style
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# license that can be found in the LICENSE file.
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# Mercurial extension to add a 'goreposum' command that
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# computes a hash of a remote repo's tag state.
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# Tag definitions can come from the .hgtags file stored in
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# any head of any branch, and the server protocol does not
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# expose the tags directly. However, the protocol does expose
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# the hashes of all the branch heads, so we can use a hash of
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# all those branch names and heads as a conservative snapshot
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# of the entire remote repo state, and use that as the tag sum.
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# Any change on the server then invalidates the tag sum,
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# even if it didn't have anything to do with tags, but at least
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# we will avoid re-cloning a server when there have been no
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# changes at all.
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#
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# Separately, this extension also adds a 'golookup' command that
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# returns the hash of a specific reference, like 'default' or a tag.
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# And golookup of a hash confirms that it still exists on the server.
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# We can use that to revalidate that specific versions still exist and
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# have the same meaning they did the last time we checked.
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#
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# Usage:
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#
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# hg --config "extensions.goreposum=$GOROOT/lib/hg/goreposum.py" goreposum REPOURL
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import base64, hashlib, sys
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from mercurial import registrar, ui, hg, node
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from mercurial.i18n import _
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cmdtable = {}
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command = registrar.command(cmdtable)
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@command(b'goreposum', [], _('url'), norepo=True)
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def goreposum(ui, url):
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"""
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goreposum computes a checksum of all the named state in the remote repo.
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It hashes together all the branch names and hashes
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and then all the bookmark names and hashes.
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Tags are stored in .hgtags files in any of the branches,
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so the branch metadata includes the tags as well.
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"""
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h = hashlib.sha256()
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peer = hg.peer(ui, {}, url)
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for name, revs in peer.branchmap().items():
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h.update(name)
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for r in revs:
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h.update(b' ')
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h.update(r)
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h.update(b'\n')
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if (b'bookmarks' in peer.listkeys(b'namespaces')):
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for name, rev in peer.listkeys(b'bookmarks').items():
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h.update(name)
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h.update(b'=')
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h.update(rev)
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h.update(b'\n')
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print('r1:'+base64.standard_b64encode(h.digest()).decode('utf-8'))
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@command(b'golookup', [], _('url rev'), norepo=True)
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def golookup(ui, url, rev):
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"""
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golookup looks up a single identifier in the repo,
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printing its hash.
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"""
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print(node.hex(hg.peer(ui, {}, url).lookup(rev)).decode('utf-8'))
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