Until now, the `gitlab`-fetcher determined the source's rev by checking
the latest commit of the given `ref` using the
`/repository/branches`-API.
This breaks however when trying to fetch a gitlab-repo by its tag:
```
$ nix repl
nix-repl> builtins.fetchTree gitlab:Ma27/nvim.nix/0.2.0
error: --- Error ------------------------------------------------------------------------------------- nix
unable to download 'https://gitlab.com/api/v4/projects/Ma27%2Fnvim.nix/repository/branches/0.2.0': HTTP error 404 ('')
```
When using the `/commits?ref_name`-endpoint[1] you can pass any kind of
valid ref to the `gitlab`-fetcher.
Please note that this fetches the only first 20 commits on a ref,
unfortunately there's currently no endpoint which only retrieves the
latest commit of any kind of `ref`.
[1] https://docs.gitlab.com/ee/api/commits.html#list-repository-commits
The `m` acts as termination-symbol when declaring graphics. Because
of this, the `;1m` doesn't have any effect and is directly printed to
the console:
```
$ nix repl
> builtins.fetchGit { /* ... */ }
{ outPath = "/nix/store/s0f0iz4a41cxx2h055lmh6p2d5k5bc6r-source"; rev = "e73e45b723a9a6eecb98bd5f3df395d9ab3633b6"; revCount = ;1m428; shortRev = "e73e45b"; submodules = ;1mfalse; }
```
Introduced by 6403508f5a.
This reduces memory consumption of
nix-instantiate \
-E 'with import <nixpkgs> {}; runCommand "foo" { src = ./blender; } "echo foo"' \
--option nar-buffer-size 10000
(where ./blender is a 1.1 GiB tree) from 1716 to 36 MiB, while still
ensuring that we don't do any write I/O for small source paths (up to
'nar-buffer-size' bytes). The downside is that large paths are now
always written to a temporary location in the store, even if they
produce an already valid store path. Thus, adding large paths might be
slower and run out of disk space. ¯\_(ツ)_/¯ Of course, you can always
restore the old behaviour by setting 'nar-buffer-size' to a very high
value.
This allows you to refer to an input from another flake. For example,
$ nix run --inputs-from /path/to/hydra nixpkgs#hello
runs 'hello' from the 'nixpkgs' inputs of the 'hydra' flake.
Fixes#3769.
Maximilian Bosch