Re: [PATCH v3 1/2] Allow using stdin in run_on_* functions

"Kevin Lyles via GitGitGadget" [off-list ref] writes:

Subject: Re: [PATCH v3 1/2] Allow using stdin in run_on_* functions

Imagine that these two commits are applied and appear among hundreds
of other commits in the list of contributions.  Would this commit
title blend in and belong to others?

    $ git log --oneline --no-merges -100

cf. Documentation/SubmittingPatches:describe-changes.

At least, it should somehow hint that the patch is about updating
the t1092 test script.

    Subject: t1092: allow run_on_* functions to use standard input

or something.

From: Kevin Lyles <redacted>

The 'run_on_sparse' and 'run_on_all' functions previously did not work
correctly for commands accepting standard input.

Our convention is to first describe the status quo in the present
tense, so "previously did not" -> "do not".

It would be helpful to explain why they do not work, perhaps like
so:

    ... functions do not work for commands that consume their
    standard input, because they attempt to run the same command in
    multiple repositories that are set up differently to inspect
    their behaviour differences.

This also indirectly
affected 'test_all_match' and 'test_sparse_match'.

"affected" -> "affects".

Now, we accept standard input and will send it to each command that we
run. This does not impact using the functions for commands that don't
need standard input.

And after presenting the observation on the status quo and pointing
out the issue we are going to address, it is our convention to write
what to do in imperative mood, as if we are ordering the codebase to
"become like so".  E.g.

    To allow these commands to consume the standard input, first
    slurp the contents fed from the standard input to a temporary
    file, and then run each attempt with its standard input
    redirected from the temporary file.  This way, these multiple
    attempts will all see the same contents from their standard
    input.

    Note that a command that does not read from the standard input
    does not have to redirect its standard input from </dev/null
    when using these run_on_* helper functions, as the standard
    input of the test environment is already connected to /dev/null.

or something, perhaps.

Mixture of word_with_underscore-and-dash-separation look unexpected;
use "run-on-sparse-input" instead, as the output files seem to be
named that way?

 	(
 		cd sparse-checkout &&
 		GIT_PROGRESS_DELAY=100000 "$@" >../sparse-checkout-out 2>../sparse-checkout-err
-	) &&
+	) <run_on_sparse-input &&
 	(
 		cd sparse-index &&
 		GIT_PROGRESS_DELAY=100000 "$@" >../sparse-index-out 2>../sparse-index-err
-	)
+	) <run_on_sparse-input

Shouldn't the temporary file be removed at the end, or are the
callers expected to live with them?  Unless the test is about
"ls-files -u" or "status", that is usually OK.