Re: [PATCH 1/1] quote: handle null and empty strings in sq_quote_buf_pretty()

"Garima Singh via GitGitGadget" <gitgitgadget@gmail.com> writes:

It would be more helpful to omit "Junio described a bug" and say what the bug is. As written, people still need to go back the list archive to read what I said in order to understand what bug was noticed by me, but you can save their time by describing the bug directly in the log message. For example:

    The sq_quote_buf_pretty() function does not emit anything when
    the incoming string is empty, but the function is to accumulate
    command line arguments, properly quoted as necessary, and the
    right way to add an argument that is an empty string is to show
    it quoted, i.e. ''.

or something like that. The credit to discoverer, if you must, can be given with

    Reported-by: ...

before your sign-off, but I do not think it is worth the trouble this time.

I do not appreciate these two new files only to test this corner case. That feels overly inefficient and unwieldy. It also hides the potential impact of the bug from readers to run *only* a unit test by using the function directly from an invented, non-real-world caller that is a program in t/helper/. It sometimes cannot be helped as some codepath is harder to trigger from the actual codepath in Git that matters in the real-world and is OK to resort to t/helper/ program, but in this particular case, with a little effort, we can find a codepath that can be used to feed an empty string to the function quite easily.

Here is what I did for example.

 $ git grep sq_quote_buf_pretty

tells me that sq_quote_quote_argv_pretty() calls it.

 $ git grep sq_quote_argv_pretty

then tells me that trace_run_command() makes a call to it. This is perfect, as we can have "git" run a command with arbitrary command line args and have trace print what it did.

So...

 $ GIT_TRACE=1 git -c "alias.foo=frotz foo '' bar" foo
 13:19:51.999614 git.c:703               trace: exec: git-foo
 13:19:51.999695 run-command.c:663       trace: run_command: git-foo
 13:19:51.999963 git.c:384               trace: alias expansion: foo => frotz foo  bar
 13:19:52.000327 git.c:703               trace: exec: git-frotz foo  bar
 13:19:52.000348 run-command.c:663       trace: run_command: git-frotz foo  bar
 expansion of alias 'foo' failed; 'frotz' is not a git command

With the bug fixed, 

 $ GIT_TRACE=1 ./git -c "alias.foo=frotz foo '' bar" foo
 13:22:16.777692 git.c:670               trace: exec: git-foo
 13:22:16.777806 run-command.c:643       trace: run_command: git-foo
 13:22:16.778084 git.c:366               trace: alias expansion: foo => frotz foo '' bar
 13:22:16.778315 git.c:670               trace: exec: git-frotz foo '' bar
 13:22:16.778329 run-command.c:643       trace: run_command: git-frotz foo '' bar
 expansion of alias 'foo' failed; 'frotz' is not a git command

we can see that the second arg to git-frotz is prettily shown.