t5520: various test cleanup

Thanks for the comments on the last round, Junio.

Please ignore the fixup patch from earlier, it has been bundled into this reroll.

Like earlier patchsets, I want to implement a feature that involves modifications to the test suite. Since that feature will probably take a while to polish up, however, let's clean up the test suite in a separate patchset first so it's not blocked by the feature work.

1/15 is a general improvement to test_rev_cmp() that will be used later in the series.

Changes since v5:

* More test_cmp_rev() cleanup

* Changed instances of "subshell" to "command substitution" where appropriate

* Change instances of "Git" to "git" when we are referring to the command

Changes since v4:

* Cleaned up test_cmp_rev() logic with suggestions from Junio

Changes since v3:

* Rebased and tested on top of v2.24.0

Changes since v2:

* Drop 't7408: replace test_must_fail test_path_is_file' since it's not a rabbit hole we want to go into right now

* Fix the output of test_cmp_rev ! when revs are actually equal

* Rebase against the latest master since this topic hasn't been picked up yet

Changes since v1:

* Incorporate Eric's feedback

Denton Liu (14):
t: teach test_cmp_rev to accept ! for not-equals
t5520: improve test style
t5520: use sq for test case names
t5520: let sed open its own input
t5520: replace test -f with test-lib functions
t5520: remove spaces after redirect operator
t5520: use test_line_count where possible
t5520: replace test -{n,z} with test-lib functions
t5520: use test_cmp_rev where possible
t5520: test single-line files by git with test_cmp
t5520: don't put git in upstream of pipe
t5520: replace $(cat ...) comparison with test_cmp
t5520: remove redundant lines in test cases
t5520: replace ! git with test_must_fail git

 t/t2400-worktree-add.sh             |   4 +-
 t/t3400-rebase.sh                   |   2 +-
 t/t3421-rebase-topology-linear.sh   |   6 +-
 t/t3430-rebase-merges.sh            |   2 +-
 t/t3432-rebase-fast-forward.sh      |   2 +-
 t/t3501-revert-cherry-pick.sh       |   2 +-
 t/t3508-cherry-pick-many-commits.sh |   2 +-
 t/t5520-pull.sh                     | 343 +++++++++++++++++-----------
 t/test-lib-functions.sh             |  20 +-
 9 files changed, 231 insertions(+), 152 deletions(-)

Range-diff against v5:
1: 85fac754e2 ! 1: 0532847787 t: teach test_cmp_rev to accept ! for not-equals

    @@ t/test-lib-functions.sh: test_must_be_empty () {
     +# provided first, that its other two parameters refer to different
     +# revisions.
      test_cmp_rev () {
    -+	local op
    ++	local op wrong_result
     +	op='='
    ++	wrong_result='different'
     +	if test $# -ge 1 && test "x$1" = 'x!'
     +	then
     +	    op='!='
    ++	    wrong_result='the same'
     +	    shift
     +	fi
      	if test $# != 2
    @@ t/test-lib-functions.sh: test_must_be_empty () {
     +
     +		if ! test "$r1" "$op" "$r2"
      		then
    -+			local comp_out
    -+			if "x$op" = 'x='
    -+			then
    -+				comp_out='different'
    -+			else
    -+				comp_out='the same'
    -+			fi
      			cat >&4 <<-EOF
     -			error: two revisions point to different objects:
    -+			error: two revisions point to $comp_out objects:
    ++			error: two revisions point to $wrong_result objects:
      			  '$1': $r1
      			  '$2': $r2
      			EOF
 2:  2b1caec3d7 =  2:  aa3f2e3395 t5520: improve test style
 3:  1aa0cdad1c =  3:  99b0fb0e1c t5520: use sq for test case names
 4:  edd4446554 =  4:  0660aa3fff t5520: let sed open its own input
 5:  c5d5966405 =  5:  00b7143b30 t5520: replace test -f with test-lib functions
 6:  6a99400ba4 =  6:  c451940c5b t5520: remove spaces after redirect operator
 7:  b7b66b13f6 =  7:  8e1c90eb70 t5520: use test_line_count where possible
 8:  07517c868c !  8:  8043b230a7 t5520: replace test -{n,z} with test-lib functions

@@ Metadata
## Commit message ##
t5520: replace test -{n,z} with test-lib functions

- When wrapping a Git command in a subshell within another command, we
- throw away the Git command's exit code. In case the Git command fails,
- we would like to know about it rather than the failure being silent.
- Extract Git commands so that their exit codes are not lost.
+ When wrapping a git command in a command substitution within another
+ command, we throw away the git command's exit code. In case the git
+ command fails, we would like to know about it rather than the failure
+ being silent. Extract git commands so that their exit codes are not
+ lost.

Instead of using test -n or test -z, replace them respectively with invocations of test_file_not_empty() and test_must_be_empty() so that we
9: 29d9ff3b21 ! 9: 7f5347bb40 t5520: use test_cmp_rev where possible
@@ Metadata
## Commit message ##
t5520: use test_cmp_rev where possible

- In case an invocation of git rev-list fails within the subshell, the
- failure will be masked. Remove the subshell and use test_cmp_rev() so
- that failures can be discovered.
+ In case an invocation of git rev-list fails within the command
+ substitution, the failure will be masked. Remove the command
+ substitution and use test_cmp_rev() so that failures can be discovered.

This change was done with the following sed expressions:

10: aeaa3374a7 ! 10: 73004d6cc3 t5520: test single-line files by git with test_cmp
@@ Metadata
## Commit message ##
t5520: test single-line files by git with test_cmp

- In case an invocation of a Git command fails within the subshell, the
- failure will be masked. Replace the subshell with a file-redirection and
- a call to test_cmp.
+ In case an invocation of a git command fails within the command
+ substitution, the failure will be masked. Replace the command
+ substitution with a file-redirection and a call to test_cmp.

This change was done with the following GNU sed expressions:

11: 131609fc5c ! 11: 463f5c11b9 t5520: don't put git in upstream of pipe
@@ Commit message

Before, if the invocation of git failed, it would be masked by the pipe since only the return code of the last element of a pipe is used.
- Rewrite the test to put the Git command on its own line so its return
+ Rewrite the test to put the git command on its own line so its return
code is not masked.

## t/t5520-pull.sh ##
12: c67be3d18c ! 12: 67ea3f0238 t5520: replace subshell cat comparison with test_cmp
@@ Metadata
Author: Denton Liu <[email protected]>

## Commit message ##
- t5520: replace subshell cat comparison with test_cmp
+ t5520: replace $(cat ...) comparison with test_cmp

We currently have many instances of test <line> = $(cat <file>) and test $(cat <file>) = <line>. In the case where this fails, it will be

13:  04ef898857 = 13:  b45c088d20 t5520: remove redundant lines in test cases
14:  153ff07dc0 ! 14:  c605afa537 t5520: replace `! git` with `test_must_fail git`

@@ Metadata
## Commit message ##
t5520: replace ! git with test_must_fail git

- Currently, if a Git command fails in an unexpected way, such as a
+ Currently, if a git command fails in an unexpected way, such as a
segfault, it will be masked and ignored. Replace the ! with test_must_fail so that only expected failures pass.

2.24.0.346.gee0de6d492