Support external git?

[GunnarFarneback]

Would it be reasonable to add a Preferences controlled option to call an external git instead of the jll?

Rationale is that I want to use the Git package for LocalRegistry but it would be nice to give the users an option to run their own git (older version, newer version, locally patched version, whatever) if they for some reason should need to.

[giordano]

You can already do it: https://docs.binarybuilder.org/stable/jll/#Overriding-the-artifacts-in-JLL-packages

[GunnarFarneback]

That's nice but I have a hard time figuring out how to use it.

I fail to get any effect at all from an Overrides.toml but I guess that's not a viable approach anyway due to

• The artifact location is held in the artifact_dir variable mentioned above, which is the "prefix" of the installation of the package. Recall the paths of the products in the JLL package is relative to artifact_dir and the files you want to use to override the products of the JLL package must have the same tree structure as the artifact. In our example we need to use /usr to override Fontconfig and /usr/local for Bzip2.

and I can't see that my system git installation matches the directory structure of the artifact.

Doing set_preferences!("LocalPreferences.toml", "Git_jll", "git_path" => "/usr/bin/git") works to an extent. It does run my system git binary, at least the reported version matches, but git --exec-path points into my artifact, which seems less than robust. This is of course related to what goes on in https://github.com/JuliaVersionControl/Git.jl/blob/master/src/git_function.jl#L24-L48 and given the structural discrepancy between the artifact and my system installation I don't see how I could get it to work.

[giordano]

You need a prefix which has git in $(prefix)/bin/git

[GunnarFarneback]

This is my attempt with Overrides:

gunnar@gunnar-ubuntu22:/tmp/test1$ which git
/usr/bin/git
gunnar@gunnar-ubuntu22:/tmp/test1$ git --version
git version 2.34.1
gunnar@gunnar-ubuntu22:/tmp/test1$ cat Overrides.toml 
[f8c6e375-362e-5223-8a59-34ff63f689eb]
Git = "/usr"
gunnar@gunnar-ubuntu22:/tmp/test1$ julia --project=.
               _
   _       _ _(_)_     |  Documentation: https://docs.julialang.org
  (_)     | (_) (_)    |
   _ _   _| |_  __ _   |  Type "?" for help, "]?" for Pkg help.
  | | | | | | |/ _` |  |
  | | |_| | | | (_| |  |  Version 1.9.3 (2023-08-24)
 _/ |\__'_|_|_|\__'_|  |  Official https://julialang.org/ release
|__/                   |

julia> using Git_jll

julia> Git_jll.artifact_dir
"/home/gunnar/.julia/artifacts/8cb25db9a73519e871cc50d6915f8ab2770096f3"

julia> using Git

julia> run(`$(Git.git()) --version`);
git version 2.42.0

and this is the result with preferences:

gunnar@gunnar-ubuntu22:/tmp/test2$ git --exec-path
/usr/lib/git-core
gunnar@gunnar-ubuntu22:/tmp/test2$ cat LocalPreferences.toml 
[Git_jll]
git_path = "/usr/bin/git"
gunnar@gunnar-ubuntu22:/tmp/test2$ julia --project=.
               _
   _       _ _(_)_     |  Documentation: https://docs.julialang.org
  (_)     | (_) (_)    |
   _ _   _| |_  __ _   |  Type "?" for help, "]?" for Pkg help.
  | | | | | | |/ _` |  |
  | | |_| | | | (_| |  |  Version 1.9.3 (2023-08-24)
 _/ |\__'_|_|_|\__'_|  |  Official https://julialang.org/ release
|__/                   |

julia> using Git

julia> run(`$(Git.git()) --version`);
git version 2.34.1

julia> run(`$(Git.git()) --exec-path`);
/home/gunnar/.julia/artifacts/8cb25db9a73519e871cc50d6915f8ab2770096f3/libexec/git-core

[giordano]

% julia --project=. -q
shell> cat LocalPreferences.toml
[Git_jll]
git_path = "/usr/bin/git"

shell> cat Project.toml
[deps]
Git_jll = "f8c6e375-362e-5223-8a59-34ff63f689eb"

julia> using Git_jll

julia> git()
setenv(`/usr/bin/git`,[...])

[giordano]

You need Git_jll explicitly as top-level dependency in your project (I've never got whether that's intentional, or a bug)

[GunnarFarneback]

I do have Git_jll as a direct dependency and I do get Git_jll.git() to point to /usr/bin/git but Git.git() sets up environment variables pointing into the artifact.

[giordano]

Ah, ok, then probably we want to opt out of all the env vars in https://github.com/JuliaVersionControl/Git.jl/blob/259dc047e11ee326b7d2cac63cb09ceeb8f4711b/src/git_function.jl if the product is overridden, as we basically trust the outer environment is appropriately set.

[staticfloat]

I think the issue is that everything is calculated based off of root which is set to artifact_dir, but you're overriding git_path. Perhaps Git.jl should base the locations off of git_path instead.

[GunnarFarneback]

What is the preferred way to determine whether it has been overridden?

(Oh, well, all this stuff seems too complicated from a user point of view. It will be less work for me to just add a keyword argument to specify a custom git than to document how people should go about changing it through Git_jll preferences.)

[GunnarFarneback]

Perhaps Git.jl should base the locations off of git_path instead.

Still seems tricky to line that up. The artifact has exec-path in ../../libexec/git-core whereas my system git has it in ../../lib/git-core.

[giordano]

Yeah, that's why I think we should just not do anything here when the artifact is overridden, but I don't know how to test that condition.

[GunnarFarneback]

You need Git_jll explicitly as top-level dependency in your project (I've never got whether that's intentional, or a bug)

I followed some bread crumbs and found that it's intentional, see second last section of JuliaLang/julia#37791 (comment).

It is a very annoying limitation.