Consolidate go.mod.sri and go.toolchain.rev.sri into a single
flakehashes.json file at the repo root, owned by a new Go program at
tool/updateflakes. The JSON is consumed by flake.nix via
builtins.fromJSON and by any future Go code via the FlakeHashes
struct that defines its schema.
Each block records its input fingerprint alongside the SRI it
produced: the goModSum (a sha256 over go.mod and go.sum) for the
vendor block, and the literal rev string from go.toolchain.rev for
the toolchain block. updateflakes regenerates a block only when its
recorded fingerprint disagrees with the current input.
Doing the gating by content rather than file mtimes avoids the usual
mtime hazards across git checkouts, clones, and merges. It also
means re-runs with no input changes are essentially free, and a
re-run that touches only one input pays only for that one block.
The two blocks have no shared state -- vendor invokes go mod vendor
into one tempdir, toolchain fetches and extracts a tarball into
another -- so they run concurrently via errgroup. Cold time is
bounded by the slower of the two rather than their sum.
Also takes the opportunity to fold the toolchain fetch into a single
curl|tar pipeline (no intermediate .tar.gz on disk).
Split cmd/nardump into a thin package main and a new package nardump
library at cmd/nardump/nardump that holds the NAR encoder and SRI
helper. tool/updateflakes imports the library directly rather than
building and exec'ing the nardump binary at runtime. The library
uses fs.ReadLink (Go 1.25+) instead of os.Readlink, so it no longer
requires the caller to chdir into the FS root for symlink targets to
resolve. WriteNAR now wraps its writer in a bufio.Writer internally
(unless the caller already passed one) and flushes on return, so
callers don't pay for tiny writes against slow underlying writers.
The cache-busting line in flake.nix and shell.nix is known to live
at end of file, so updateCacheBust walks the lines in reverse.
make tidy timings on this machine, before: ~14s every run.
After:
warm (no input changes): 0.05s
vendor block stale only: 1.4s
toolchain block stale only: 5.0s
cold (no flakehashes.json): 5.0s
Updates #6845
Change-Id: I0340608798f1614abf147a491bf7c68a198a0db4
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
This file was never truly necessary and has never actually been used in
the history of Tailscale's open source releases.
A Brief History of AUTHORS files
---
The AUTHORS file was a pattern developed at Google, originally for
Chromium, then adopted by Go and a bunch of other projects. The problem
was that Chromium originally had a copyright line only recognizing
Google as the copyright holder. Because Google (and most open source
projects) do not require copyright assignemnt for contributions, each
contributor maintains their copyright. Some large corporate contributors
then tried to add their own name to the copyright line in the LICENSE
file or in file headers. This quickly becomes unwieldy, and puts a
tremendous burden on anyone building on top of Chromium, since the
license requires that they keep all copyright lines intact.
The compromise was to create an AUTHORS file that would list all of the
copyright holders. The LICENSE file and source file headers would then
include that list by reference, listing the copyright holder as "The
Chromium Authors".
This also become cumbersome to simply keep the file up to date with a
high rate of new contributors. Plus it's not always obvious who the
copyright holder is. Sometimes it is the individual making the
contribution, but many times it may be their employer. There is no way
for the proejct maintainer to know.
Eventually, Google changed their policy to no longer recommend trying to
keep the AUTHORS file up to date proactively, and instead to only add to
it when requested: https://opensource.google/docs/releasing/authors.
They are also clear that:
> Adding contributors to the AUTHORS file is entirely within the
> project's discretion and has no implications for copyright ownership.
It was primarily added to appease a small number of large contributors
that insisted that they be recognized as copyright holders (which was
entirely their right to do). But it's not truly necessary, and not even
the most accurate way of identifying contributors and/or copyright
holders.
In practice, we've never added anyone to our AUTHORS file. It only lists
Tailscale, so it's not really serving any purpose. It also causes
confusion because Tailscalars put the "Tailscale Inc & AUTHORS" header
in other open source repos which don't actually have an AUTHORS file, so
it's ambiguous what that means.
Instead, we just acknowledge that the contributors to Tailscale (whoever
they are) are copyright holders for their individual contributions. We
also have the benefit of using the DCO (developercertificate.org) which
provides some additional certification of their right to make the
contribution.
The source file changes were purely mechanical with:
git ls-files | xargs sed -i -e 's/\(Tailscale Inc &\) AUTHORS/\1 contributors/g'
Updates #cleanup
Change-Id: Ia101a4a3005adb9118051b3416f5a64a4a45987d
Signed-off-by: Will Norris <will@tailscale.com>
This updates all source files to use a new standard header for copyright
and license declaration. Notably, copyright no longer includes a date,
and we now use the standard SPDX-License-Identifier header.
This commit was done almost entirely mechanically with perl, and then
some minimal manual fixes.
Updates #6865
Signed-off-by: Will Norris <will@tailscale.com>
