Fixes#8309
This regression was because both `CmdDevelop` and `CmdPrintDevEnv` were
switched to be `InstallableValueCommand` subclasses, but actually
neither should have been.
The `nixpkgsFlakeRef` method should indeed not be on the base
installable class, because "flake refs" and "nixpkgs" are not
installable-wide notions, but that doesn't mean these commands should
only accept installable values.
This fixes a bug in commands like `nix eval' which would emit invalid attribute
sets if they contained reserved keywords such as "assert", "let", etc.
These keywords will not be quoted when printed, making them valid expressions.
All keywords recognized by the lexer are quoted except "or", which does not
require quotation.
it's probably better not to show the manifest file documentation in the
command-specific pages, because these are implementation details that are not really practically useful.
this means no additional hassle for building the manual, but clutters
the table of contents a bit.
Previously, we relied on the `shutdown()` function to terminate `accept()`
calls on a listening socket. However, this approach did not work on macOS as
the waiting `accept()` call is not considered a connected socket, resulting in
an `ENOTCONN` error. Instead, we now close the listening socket to terminate
the `accept()` call.
Additionally, we fixed a resource management issue where we set the
`daemonSocket` variable to -1, triggering resource cleanup and causing the
`stopDaemon` function to be called twice. This resulted in errors as the socket
was already closed by the time the second `stopDaemon` call was made. Instead of
setting `daemonSocket` to -1, we now release the socket using the `release()`
method on a unique pointer. This properly transfers ownership and allows for
correct resource cleanup.
These changes ensure proper behavior and resource management for the
recursive-nix feature on macOS.
Motivation
`PathSet` is not correct because string contexts have other forms
(`Built` and `DrvDeep`) that are not rendered as plain store paths.
Instead of wrongly using `PathSet`, or "stringly typed" using
`StringSet`, use `std::std<StringContextElem>`.
-----
In support of this change, `NixStringContext` is now defined as
`std::std<StringContextElem>` not `std:vector<StringContextElem>`. The
old definition was just used by a `getContext` method which was only
used by the eval cache. It can be deleted altogether since the types are
now unified and the preexisting `copyContext` function already suffices.
Summarizing the previous paragraph:
Old:
- `value/context.hh`: `NixStringContext = std::vector<StringContextElem>`
- `value.hh`: `NixStringContext Value::getContext(...)`
- `value.hh`: `copyContext(...)`
New:
- `value/context.hh`: `NixStringContext = std::set<StringContextElem>`
- `value.hh`: `copyContext(...)`
----
The string representation of string context elements no longer contains
the store dir. The diff of `src/libexpr/tests/value/context.cc` should
make clear what the new representation is, so we recommend reviewing
that file first. This was done for two reasons:
Less API churn:
`Value::mkString` and friends did not take a `Store` before. But if
`NixStringContextElem::{parse, to_string}` *do* take a store (as they
did before), then we cannot have the `Value` functions use them (in
order to work with the fully-structured `NixStringContext`) without
adding that argument.
That would have been a lot of churn of threading the store, and this
diff is already large enough, so the easier and less invasive thing to
do was simply make the element `parse` and `to_string` functions not
take the `Store` reference, and the easiest way to do that was to simply
drop the store dir.
Space usage:
Dropping the `/nix/store/` (or similar) from the internal representation
will safe space in the heap of the Nix programming being interpreted. If
the heap contains many strings with non-trivial contexts, the saving
could add up to something significant.
----
The eval cache version is bumped.
The eval cache serialization uses `NixStringContextElem::{parse,
to_string}`, and since those functions are changed per the above, that
means the on-disk representation is also changed.
This is simply done by changing the name of the used for the eval cache
from `eval-cache-v4` to eval-cache-v5`.
----
To avoid some duplication `EvalCache::mkPathString` is added to abstract
over the simple case of turning a store path to a string with just that
string in the context.
Context
This PR picks up where #7543 left off. That one introduced the fully
structured `NixStringContextElem` data type, but kept `PathSet context`
as an awkward middle ground between internal `char[][]` interpreter heap
string contexts and `NixStringContext` fully parsed string contexts.
The infelicity of `PathSet context` was specifically called out during
Nix team group review, but it was agreeing that fixing it could be left
as future work. This is that future work.
A possible follow-up step would be to get rid of the `char[][]`
evaluator heap representation, too, but it is not yet clear how to do
that. To use `NixStringContextElem` there we would need to get the STL
containers to GC pointers in the GC build, and I am not sure how to do
that.
----
PR #7543 effectively is writing the inverse of a `mkPathString`,
`mkOutputString`, and one more such function for the `DrvDeep` case. I
would like that PR to have property tests ensuring it is actually the
inverse as expected.
This PR sets things up nicely so that reworking that PR to be in that
more elegant and better tested way is possible.
Co-authored-by: Théophane Hufschmitt <7226587+thufschmitt@users.noreply.github.com>
In other words, use a plain `ContentAddress` not
`ContentAddressWithReferences` for `DerivationOutput::CAFixed`.
Supporting fixed output derivations with (fixed) references would be a
cool feature, but it is out of scope at this moment.
Recently, I encountered the "NAR info file 'xxxx' is corrupt" error
with my binary cache. The message is not helpful in determining, which
kind of corruption happened. The file, fetched with curl, looked
reasonably.
This commit adds more information to the error message, which should
allow debugging and hopefully fixing the problem.
We finally test the status quo of remote build trust in a number of
ways. We create a new experimental feature on `nix-daemon` to do so.
PR #3921, which improves the situation with trustless remote building,
will build upon these changes. This code / tests was pull out of there
to make this, so everything is easier to review, and in particular we
test before and after so the new behavior in that PR is readily apparent
from the testsuite diff alone.
Issues:
1. Features gated on disabled experimental settings should warn and be
ignored, not silently succeed.
2. Experimental settings in the same config "batch" (file or env var)
as the enabling of the experimental feature should work.
3. For (2), the order should not matter.
These are analogous to the issues @roberth caught with my changes for
arg handling, but they are instead for config handling.
Co-authored-by: Robert Hensing <roberth@users.noreply.github.com>
In many cases we are dealing with a collection of realisations, they are
all outputs of the same derivation. In that case, we don't need
"derivation hashes modulos" to be part of our map key, because the
output names alone will be unique. Those hashes are still part of the
realisation proper, so we aren't loosing any information, we're just
"normalizing our schema" by narrowing the "primary key".
Besides making our data model a bit "tighter" this allows us to avoid a
double `for` loop in `DerivationGoal::waiteeDone`. The inner `for` loop
was previously just to select the output we cared about without knowing
its hash. Now we can just select the output by name directly.
Note that neither protocol is changed as part of this: we are still
transferring `DrvOutputs` over the wire for `BuildResult`s. I would only
consider revising this once #6223 is merged, and we can mention protocol
versions inside factored-out serialization logic. Until then it is
better not change anything because it would come a the cost of code
reuse.
If my memory is correct, @edolstra objected to modifying `wantedOutputs`
upon falling back to doing a build (as we did before), because we should
only modify it in response to new requests --- *actual* wants --- and
not because we are "incidentally" building all the outptus beyond what
may have been requested.
That's a fair point, and the alternative is to replace the boolean soup
with proper enums: Instead of modifying `wantedOuputs` som more, we'll
modify `needsRestart` to indicate we are passed the need.
In https://github.com/NixOS/nix/pull/6311#discussion_r834863823, I
realized since derivation goals' wanted outputs can "grow" due to
overlapping dependencies (See `DerivationGoal::addWantedOutputs`, called
by `Worker::makeDerivationGoalCommon`), the previous bug fix had an
unfortunate side effect of causing more pointless rebuilds.
In paticular, we have this situation:
1. Goal made from `DerivedPath::Built { foo, {a} }`.
2. Goal gives on on substituting, starts building.
3. Goal made from `DerivedPath::Built { foo, {b} }`, in fact is just
modified original goal.
4. Though the goal had gotten as far as building, so all outputs were
going to be produced, `addWantedOutputs` no longer knows that and so
the goal is flagged to be restarted.
This might sound far-fetched with input-addressed drvs, where we usually
basically have all our goals "planned out" before we start doing
anything, but with CA derivation goals and especially RFC 92, where *drv
resolution* means goals are created after some building is completed, it
is more likely to happen.
So the first thing to do was restore the clearing of `wantedOutputs` we
used to do, and then filter the outputs in `buildPathsWithResults` to
only get the ones we care about.
But fix also has its own side effect in that the `DerivedPath` in the
`BuildResult` in `DerivationGoal` cannot be trusted; it is merely the
*first* `DerivedPath` for which this goal was originally created.
To remedy this, I made `BuildResult` be like it was before, and instead
made `KeyedBuildResult` be a subclass wit the path. Only
`buildPathsWithResults` returns `KeyedBuildResult`s, everything else
just becomes like it was before, where the "key" is unambiguous from
context.
I think separating the "primary key" field(s) from the other fields is
good practical in general anyways. (I would like to do the same thing
for `ValidPathInfo`.) Among other things, it allows constructions like
`std::map<Key, ThingWithKey>` where doesn't contain duplicate keys and
just precludes the possibility of those duplicate keys being out of
sync.
We might leverage the above someday to overload `buildPathsWithResults`
to take a *set* of return a *map* per the above.
-----
Unfortunately, we need to avoid C++20 strictness on designated
initializers.
(BTW
https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2021/p2287r1.html
this offers some new syntax for this use-case. Hopefully this will be
adopted and we can eventually use it.)
No having that yet, maybe it would be better to not make
`KeyedBuildResult` a subclass to just avoid this.
Co-authored-by: Robert Hensing <roberth@users.noreply.github.com>
As requested by @roberth, it is good to call out the specific instances
we care about, which is `!` for the RPC protocols, and `^` for humans.
This doesn't take advantage of parametricity as much, but since the
human and computer interfaces are good to decouple anyways (we don't
care if they drift further apart over time in the slightest) some
separation and slight duplication is fine.
Also, unit test both round trips.
More progress on issue #5729
The method trivially generalizes to be store-implementation-agnostic, in
fact.
However, we force it to continue to be unimplemented with `RemoteStore`
and `LegacySSHStore` because the implementation we'd get via the
generalization is probably not the one users expect. This keeps our
hands untied to do it right going forward.
For more about the tension between the scheduler logic being
store-type-agnostic and remote stores doing their own scheduling, see
issues #5025 and #5056.
- Create a glossary entry for experimental features.
- Have the man page experimental feature notice link `nix-commmand`.
(Eventually this should be programmed, based on whether the command is
experimental, and if so what experimental feature does it depend on.)
- Document which installables depend on which experimental features.
I tried to use the same style (bold warning and block quote) that the
top of the man page uses.
Co-authored-by: Valentin Gagarin <valentin.gagarin@tweag.io>
The warning message should produce an installable name that can be
passed to `nix build`, `nix path-info`, etc. again. Since the CLI
expects that the .drv path and the output names are separated by
a caret, the warning message must also separate the .drv path and output
names with a caret.
However, `DerivedPath::Built.to_string()` uses an exclamation point as
the separator instead. This commit adds a `separator` argument to the
to_string method.
This changes the warning message from:
If this command is now failing try again with '/nix/store/foo.drv!*'
to:
If this command is now failing try again with '/nix/store/foo.drv^*'
More progress on issue #5729.
Instead of having it by the default method in `Store` itself, have it be
the implementation in `DummyStore` and `LegacySSHStore`. Then just the
implementations which fail to provide the method pay the "penalty" of
dealing with the icky `unimplemented` function for non-compliance.
Combined with my other recent PRs, this finally makes `Store` have no
`unsupported` calls!
This is somewhat hacky fix just for 2.15. I unintentionally hid them
from the manual, when no one wanted to hide them that (including
myself). I also required the experimental feature to be enabled in an
order-dependent way, which is not good.
The simplest fix for this immanent release is just to always show them,
and always allow them to be set.
Effectively undoes some changes from aa663b7e89
Getting the occasional SQLITE_BUSY is expected when the database is being
accessed concurrently. The retry will likely succeed so it is pointless to warn
immediately. Instead we track how long each retrySQLite block has been running,
and only begin warning after a second has elapsed (and then every 10 seconds
subsequently).
Some of the factoring out was taken from #7912 by @mupdt. Thanks!
No behavior should be changed in this commit.
Co-Authored-By: mupdt <25388474+mupdt@users.noreply.github.com>
Co-authored-by: Robert Hensing <roberth@users.noreply.github.com>
How signals should be handled depends on what kind of process Nix
is integrated into. The signal handler thread used by the stand-alone
Nix commands / processes may not work well in the context of other
runtime systems, such as those of Python, Perl, or Haskell.
libutil is a dependency of libstore, so it should always be
initialized as such.
libutil is also a dependency of libmain. Being explicit about this
dependency might be good, but not worth the slight code complexity
until the library structure gets more advanced.
Part of an effort to make it easier to initialize the right things,
by moving code into the appropriate libraries.
Quote
Why not initLibExpr()? initGC() is essentially that, but
detectStackOverflow is not an instance of the init function concept, as
it may have to be invoked more than once per process.
Furthermore, renaming initGC to initLibExpr is more trouble than it's
worth at this time.
This code is bad. We shouldn't unset variables in programs whose
children may need them. Fixing one issue at a time, so postponing.
See https://github.com/NixOS/nix/issues/7731
Part of an effort to make it easier to initialize the right things,
by moving code into the appropriate libraries.
It is required for the sandbox, which is a libstore responsibility;
not just libmain.
Part of an effort to make it easier to initialize the right things,
by moving code into the appropriate libraries.
Part of an effort to make it easier to initialize the right things,
by moving code into the appropriate libraries.
The goal of this reordering is to make initLibStore self-sufficient
in a following commit.
Part of an effort to make it easier to initialize the right things,
by moving code into the appropriate libraries.
Using libstore without loading the config file is risky, as sqlite
may then be misconfigured. See https://github.com/cachix/cachix/issues/475
* Finish converting existing comments for internal API docs
99% of this was just reformatting existing comments. Only two exceptions:
- Expanded upon `BuildResult::status` compat note
- Split up file-level `symbol-table.hh` doc comments to get
per-definition docs
Also fixed a few whitespace goofs, turning leading tabs to spaces and
removing trailing spaces.
Picking up from #8133
* Fix two things from comments
* Use triple-backtick not indent for `dumpPath`
* Convert GNU-style `\`..'` quotes to markdown style in API docs
This will render correctly.
This is non-breaking change in the to-JSON direction. This *is* a
breaking change in the from-JSON direction, but we don't care, as that
is brand new in this PR.
`nix show-derivation --help` currently has the sole public documentation
of this format, it is updated accordingly.
The `write` name is ambiguous and could lead to some funny bugs like
https://github.com/NixOS/nix/pull/8173#issuecomment-1500009480. So
rename it to the more explicit `writeUnbuffered`.
Besides, this method shouldn't be (and isn't) used outside of the class
implementation, so mark it `protected`.
This makes it more symetrical to `BufferedSource` which uses a
`protected readUnbuffered` method.
This function returns true or false depending on whether the Nix client
is trusted or not. Mostly relevant when speaking to a remote store with
a daemon.
We include this information in `nix ping store` and `nix doctor`
Co-Authored-By: John Ericson <John.Ericson@Obsidian.Systems>
They are put in the manual separate pages under the new overarching
description of experimental features.
The settings page just lists the valid experimental feature names (so
people know what a valid setting entry looks like), with links to those
pages. It doesn't attempt to describe each experimental feature as that
is too much information for the configuration settings section.
This introduces the SourcePath type from lazy-trees as an abstraction
for accessing files from inputs that may not be materialized in the
real filesystem (e.g. Git repositories). Currently, however, it's just
a wrapper around CanonPath, so it shouldn't change any behaviour. (On
lazy-trees, SourcePath is a <InputAccessor, CanonPath> tuple.)
Instead of constructing a markdown list in C++ (which involved all sorts
of nasty string literals), export some JSON and assemble it with the
manual build system.
Besides following the precedent set with other dumped data, this is a
better separate of content and presentation; if we decide for example we
want to display this information in a different way, or in a different
section of the manual, it will become much easier to do so.
switch statements must now match all enum values or disable the
warning.
Explicit is good. This has helped us find two bugs, after solving
another one by debugging.
From now on, adding to an enum will raise errors where they are
not explicitly handled, which is good for productivity, and helps
us decide the correct behavior in all usages.
Notably still excluded from this though are the cases where the
warning is disabled by local pragmas.
fromTOML.cc did not build despite a top-level pragma, so I've had
to resort to a makefile solution for that.
Prior to this, there was an ad-hoc whitelist in `main.cc`. Now, every
command states its stability.
In a future PR, we will adjust the manual to take advantage of this new
information in the JSON.
(It will be easier to do that once we have some experimental feature
docs to link too; see #5930 and #7798.)
The code is not local-store-specific, so we should share it with all
stores. More uniform behavior is better, and a less store-specific
functionality is more maintainable.
This fixes a FIXME added in f73d911628 by @edolstra himself.
Documentation on "classic" commands with many sub-commands are
notoriously hard to discover due to lack of overview and anchor links.
Additionally the information on common options and environment variables
is not accessible offline in man pages, and therefore often overlooked
by readers.
With this change, each sub-command of nix-store and nix-env gets its
own page in the manual (listed in the table of contents), and each own
man page.
Also, man pages for each subcommand now (again) list common options
and environment variables. While this makes each page quite long and
some common parameters don't apply, this should still make it easier
to navigate as that additional information was not accessible on the
command line at all.
It is now possible to run 'nix-store --<subcommand> --help` to display
help pages for the given subcommand.
Co-authored-by: Valentin Gagarin <valentin.gagarin@tweag.io>
This fixes the issue that `nix-build`, without experimental feature
'nix-command' enabled, recommends the experimental CLI `nix log` to view
build logs. Now it'll recommend the stable `nix-store -l` CLI instead.
Fixes https://github.com/NixOS/nix/issues/8118
See the note in the test.
We don't want these flags showing up for commands where they are
irrelevant.
Eventually, this needs a proper fix, but it need not be a blocker for
stabilize: for a quick-n-dirty punt, just put these flags behind the
`nix-command` unstable feature.
This is fine because they are only relevant for commands which we don't
need to stabilize for a while.
`legacyPackages` of nixpkgs trigger eval errors in `hasContent`, causing
the whole `legacyPackages` being skipped. We should treat it as
has-content in that case.
Instead of having a bunch of optional fields, have a few subclasses
which can have mandatory fields.
Additionally, the new `getExtraPathInfo`, and `nixpkgsFlakeRef`, are
moved to `InstallableValue`.
I did these things because https://github.com/NixOS/rfcs/pull/134 ; with
these things moved to `InstallableValue`, the base `Installable` no
longer depends on libexpr! This is a major step towards that.
Also, add a bunch of doc comments for sake of the internal API docs.
Otherwise, a trace consisting of
frame
frame
frame
non-frame
... would reach the non-frame and print the suggestion, even though
it would have ignored the non-frame anyway.
This resulted in a peculariar situation where --show-trace would have
no apparent effect, as the trace was actually already complete.
Pause logger before starting SSH connections, and resume it after the
connection is established, so that SSH password prompts are not erased
by the logger's updates.
Otherwise, when running as root and user namespaces are enabled,
opening the slave fails with EPERM.
Fixes "opening pseudoterminal slave: Permission denied" followed by a
hang (https://hydra.nixos.org/build/213104244), and "error: getting
sandbox mount namespace: No such file or directory" (#8072), which
happens when the child fails very quickly and consequently reading
/proc/<child>/ns fails.
If we conditionally "declare" the argument, as we did before, based upon
weather the feature is enabled, commands like
nix --experimental-features=foo ... --thing-gated-on-foo
won't work, because the experimental feature isn't enabled until *after*
we start parsing.
Instead, allow arguments to also be associated with experimental
features (just as we did for builtins and settings), and then the
command line parser will filter out the experimental ones.
Since the effects of arguments (handler functions) are performed right
away, we get the required behavior: earlier arguments can enable later
arguments enabled!
There is just one catch: we want to keep non-positional
flags...non-positional. So if
nix --experimental-features=foo ... --thing-gated-on-foo
works, then
nix --thing-gated-on-foo --experimental-features=foo ...
should also work.
This is not my favorite long-term solution, but for now this is
implemented by delaying the requirement of needed experimental features
until *after* all the arguments have been parsed.
We hide them in various ways if the experimental feature isn't enabled.
To do this, we had to move the experimental features list out of
libnixstore, because the setting machinary itself depends on it. To do
that, we made a new `ExperimentalFeatureSettings`.
This provides a platform-independent way to configure the SSL
certificates file in the Nix daemon. Previously we provided
instructions for overriding the environment variable in launchd, but
that obviously doesn't work with systemd. Now we can just tell users
to add
ssl-cert-file = /etc/ssl/my-certificate-bundle.crt
to their nix.conf.
These methods would previously fail on the other `Installable`s, so
moving them to this class is more correct as to where they actually
work.
Additionally, a `InstallableValueCommand` is created to make it easier
(or rather no worse than before) to write commands that just work on
`InstallableValue`s.
Besides being a cleanup to avoid failing default methods, this gets us
closer to https://github.com/NixOS/rfcs/pull/134.
Already, we had classes like `BuiltPathsCommand` and `StorePathsCommand`
which provided alternative `run` virtual functions providing the
implementation with more arguments. This was a very nice and easy way to
make writing command; just fill in the virtual functions and it is
fairly clear what to do.
However, exception to this pattern were `Installable{,s}Command`. These
two classes instead just had a field where the installables would be
stored, and various side-effecting `prepare` and `load` machinery too
fill them in. Command would wish out those fields.
This isn't so clear to use.
What this commit does is make those command classes like the others,
with richer `run` functions.
Not only does this restore the pattern making commands easier to write,
it has a number of other benefits:
- `prepare` and `load` are gone entirely! One command just hands just
hands off to the next.
- `useDefaultInstallables` because `defaultInstallables`. This takes
over `prepare` for the one case that needs it, and provides enough
flexiblity to handle `nix repl`'s idiosyncratic migration.
- We can use `ref` instead of `std::shared_ptr`. The former must be
initialized (so it is like Rust's `Box` rather than `Option<Box>`,
This expresses the invariant that the installable are in fact
initialized much better.
This is possible because since we just have local variables not
fields, we can stop worrying about the not-yet-initialized case.
- Fewer lines of code! (Finally I have a large refactor that makes the
number go down not up...)
- `nix repl` is now implemented in a clearer way.
The last item deserves further mention. `nix repl` is not like the other
installable commands because instead working from once-loaded
installables, it needs to be able to load them again and again.
To properly support this, we make a new superclass
`RawInstallablesCommand`. This class has the argument parsing and
completion logic, but does *not* hand off parsed installables but
instead just the raw string arguments.
This is exactly what `nix repl` needs, and allows us to instead of
having the logic awkwardly split between `prepare`,
`useDefaultInstallables,` and `load`, have everything right next to each
other. I think this will enable future simplifications of that argument
defaulting logic, but I am saving those for a future PR --- best to keep
code motion and more complicated boolean expression rewriting separate
steps.
The "diagnostic ignored `-Woverloaded-virtual`" pragma helps because C++
doesn't like our many `run` methods. In our case, we don't mind the
shadowing it all --- it is *intentional* that the derived class only
provides a `run` method, and doesn't call any of the overridden `run`
methods.
Helps with https://github.com/NixOS/rfcs/pull/134
Add the --base64 and --sri flags for the Base64 and SRI format output.
Add the --base16 flag to explicitly specify the hexadecimal format.
Add the --to-base64 and --to-sri flag to convert a hash to the above
mentioned format.
Hopefully this fixes "unexpected EOF" failures on macOS
(#3137, #3605, #7242, #7702).
The problem appears to be that under some circumstances, macOS
discards the output written to the slave side of the
pseudoterminal. Hence the parent never sees the "sandbox initialized"
message from the child, even though it succeeded. The conditions are:
* The child finishes very quickly. That's why this bug is likely to
trigger in nix-env tests, since that uses a builtin builder. Adding
a short sleep before the child exits makes the problem go away.
* The parent has closed its duplicate of the slave file
descriptor. This shouldn't matter, since the child has a duplicate
as well, but it does. E.g. moving the close to the bottom of
startBuilder() makes the problem go away. However, that's not a
solution because it would make Nix hang if the child dies before
sending the "sandbox initialized" message.
* The system is under high load. E.g. "make installcheck -j16" makes
the issue pretty reproducible, while it's very rare under "make
installcheck -j1".
As a fix/workaround, we now open the pseudoterminal slave in the
child, rather than the parent. This removes the second condition
(i.e. the parent no longer needs to close the slave fd) and I haven't
been able to reproduce the "unexpected EOF" with this.
This allows having multiple separate lockfiles for a single
project, which can be useful for testing against different versions of
nixpkgs; it also allows tracking custom input overrides for remote
flakes without requiring local clones of these flakes.
For example, if I want to build Nix against my locally pinned nixpkgs,
and have a lock file tracking this override independently of future
updates to said nixpkgs:
nix flake lock --output-lock-file /tmp/nix-flake.lock --override-input nixpkgs flake:nixpkgs
nix build --reference-lock-file /tmp/nix-flake.lock
Co-Authored-By: Will Fancher <elvishjerricco@gmail.com>
