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git's directory is _prepended_ to PATH when called with an absolute path

DISCUSSION David Rodríguez 4 participants 9 messages Jun 15, 2016

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David Rodríguez

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#0 lore raw

For example, if I run git using:

$ /usr/bin/git

then /usr/bin is prepended to the path. Is this intentional? If it is, why?

This causes issues with Ruby git hooks, because Ruby version managers rely on custom settings in PATH to select the Ruby executable, and there's usually a system Ruby living in /usr/bin. See https://github.com/github/hub/issues/855 for an example.

Thanks a lot,

David Rodríguez.

#1 lore raw

On Tue, 21 Apr 2015 18:37:29 +0000, David Rodríguez wrote:
...

Quoted 2 lines

This causes issues with Ruby git hooks, because Ruby version managers rely on custom settings in PATH to select the Ruby executable,

Even if git wouldn't modify PATH this is still a broken way to do that. What ruby to execute a hook with is a property of the hook, not of the user context invoking it.

Andreas

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"Totally trivial. Famous last words."
From: Linus Torvalds <torvalds@*.org>
Date: Fri, 22 Jan 2010 07:29:21 -0800
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#2 lore raw
Quoted 10 lines · Andreas Krey

On Tue, 21 Apr 2015 18:37:29 +0000, David Rodríguez wrote:
...

Quoted 2 lines

This causes issues with Ruby git hooks, because Ruby version managers rely on custom settings in PATH to select the Ruby executable,

Even if git wouldn't modify PATH this is still a broken way to do that. What ruby to execute a hook with is a property of the hook, not of the user context invoking it.

Andreas

I probably shouldn't have mentioned Ruby version managers since they are not directly related to this issue. I'll try to elaborate on the issue:

* User is relying on a custom path to select their Ruby version. For example, let's say the first folder in path is "~/.rubies/2.2.2/bin".
* User runs "/usr/bin/git commit" and a pre-commit hook is triggered.
* The pre-commit hook starts with "#!/us/bin/env ruby" to select the Ruby to be used in the hook, but since the path has been changed by "/usr/bin/git", the selected ruby will be "/usr/bin/ruby" and not "~/.rubies/2.2.2/bin/ruby" as the user would expect.

What's the proper way to do whatever you're saying is done in "a broken way"?

#3 lore raw

On Wed, 22 Apr 2015 08:36:00 +0000, David Rodríguez wrote:
...

Quoted 5 lines

* User is relying on a custom path to select their Ruby version. For example, let's say the first folder in path is "~/.rubies/2.2.2/bin".
* User runs "/usr/bin/git commit" and a pre-commit hook is triggered.
* The pre-commit hook starts with "#!/us/bin/env ruby" to select the Ruby to be used in the hook,

Yes...but shouldn't the hook itself know which ruby version it needs?

After all, if I go into that directory with another ruby setup in my PATH, the hook should still work, and presumably that requires that the hook itself selects its version, and not the user's context.

Andreas

Signature · 3 lines
"Totally trivial. Famous last words."
From: Linus Torvalds <torvalds@*.org>
Date: Fri, 22 Jan 2010 07:29:21 -0800
#4 lore raw
Quoted 8 lines · Andreas Krey

On Wed, 22 Apr 2015 08:36:00 +0000, David Rodríguez wrote:
...

Quoted 5 lines

* User is relying on a custom path to select their Ruby version. For example, let's say the first folder in path is "~/.rubies/2.2.2/bin".
* User runs "/usr/bin/git commit" and a pre-commit hook is triggered.
* The pre-commit hook starts with "#!/us/bin/env ruby" to select the Ruby to be used in the hook,

Quoted 5 lines

Yes...but shouldn't the hook itself know which ruby version it needs?

After all, if I go into that directory with another ruby setup in my PATH, the hook should still work, and presumably that requires that the hook itself selects its version, and not the user's context.

More generally, #!/usr/bin/env ruby is saying, "I want whatever ruby the user chooses." If you want a ruby that has certain gems, or certain features (e.g. Array#to_h), then that's not what you want. #!/usr/bin/env ruby is basically only safe if you're willing to accept any potential version that might show up.

You can use a multiline shebang[0] if you need to execute shell code to make the decision at runtime, such as if you need to use $HOME in the path to your ruby, or select from multiple different options.

[0] http://rosettacode.org/wiki/Multiline_shebang

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brian m. carlson / brian with sandals: Houston, Texas, US
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#5 lore raw
Quoted 2 lines · brian m. carlson

"I want whatever ruby the
user chooses."

This is exactly what I want. The problem is that git overrides the user's choice by prepending /usr/bin to the path and thus making /usr/bin/env choose system's ruby version. Which is almost always not the Ruby the user chose.