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Re: [PATCH] run-command.c: print env vars when GIT_TRACE is set

On Thu, Jan 11, 2018 at 5:07 PM, Jeff King <peff@xxxxxxxx> wrote:
> On Wed, Jan 10, 2018 at 05:48:35PM +0700, Nguyễn Thái Ngọc Duy wrote:
>> Occasionally submodule code could execute new commands with GIT_DIR set
>> to some submodule. GIT_TRACE prints just the command line which makes it
>> hard to tell that it's not really executed on this repository.
>> Print env variables in this case. Note that the code deliberately ignore
>> variables unsetting because there are so many of them (to keep git
>> environment clean for the next process) and really hard to read.
> I like this, and I'm pretty sure it would have helped me debug at least
> once in the past. I did notice one funny thing, though I think it was
> largely there before.
> The output for a single command is pretty shell-like due to the quoting:
>   $ GIT_TRACE=1 ./git upload-pack . >/dev/null
>   [...]run_command: 'git-upload-pack' '.'
> You could copy and paste that to a shell if you wanted.  And with
> environment variables, that remains so:
>   $ GIT_TRACE=1 ./git ls-remote https://github.com/git/git >/dev/null
>   [...]run_command: 'GIT_DIR=.git' 'git-remote-https' 'https://[...]'
> But if we're actually running a command via the shell, it all gets
> quoted as one argument:
>   $ GIT_TRACE=1 GIT_PAGER='foo | bar' ./git log
>   [...]run_command: 'LV=-c' 'foo | bar'
> which is kind of weird, as that's not something that can be run in a
> shell. This isn't introduced by your patch at all, but I noticed it more
> because of the shell-like environment variable output.

I think you just found an argument to change my "meh" with regards to
quoting to "need to fix" because I also often copy/paste these
commands. I thought about it and assumed shells would still recognize
'name=value' assignments without actually testing it.

> We actually used to print a separate:
>   exec: /bin/sh -c 'foo | bar'
> line when we invoked a shell, which would arguably be the right place to
> show the env variables for such a case. But that went away with
> 3967e25be1 (run-command: prepare command before forking, 2017-04-19).
> I think it might be helpful if we added back in "/bin/sh -c" to the
> run_command line when "use_shell" is in effect (and when we're not doing
> our "skip the shell" trickery).  But that's totally orthogonal to your
> patch.
> And anyway, it's just tracing output, so I don't think it's incredibly
> important either way. It was just something I noticed while looking at
> your patch's output.

Noted. I might do it if it's not super complex.