[PATCH v2 0/3] test-lib-functions.sh: keep user's HOME, TERM and SHELL for 'test_pause' and 'debug'

Changes since v1:

 * added 1/3 as a preliminary step to use TEST_SHELL_PATH in test_pause
   instead of SHELL_PATH, as suggested by Carlos
 * implemented the change in behaviour through optional flags in both
   test_pause and debug. This seemed to be the simplest way to keep the
   current behaviour but also provide a way to improve the UX.

v1: This series proposes two small quality-of-life improvements (in my opinion) to the 'test_pause' and 'debug' test functions: using the original values of HOME and TERM (before they are changed by the test framework) and using SHELL instead of SHELL_PATH.

The later might be too big of a change, but I think it makes sense. We could add a new GIT_TEST_* to conditionnaly change the behaviour, but I kept it simple for v1.

Cheers, Philippe.

Philippe Blain (3):
  test-lib-functions: use 'TEST_SHELL_PATH' in 'test_pause'
  test-lib-functions: optionally keep HOME, TERM and SHELL in
    'test_pause'
  test-lib-functions: optionally keep HOME and TERM in 'debug'

 t/test-lib-functions.sh | 91 ++++++++++++++++++++++++++++++++++-------
 t/test-lib.sh           |  6 ++-
 2 files changed, 80 insertions(+), 17 deletions(-)

base-commit: 225bc32a989d7a22fa6addafd4ce7dcd04675dbf
Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-1022%2Fphil-blain%2Ftest-pause-and-debug-easier-v2
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-1022/phil-blain/test-pause-and-debug-easier-v2
Pull-Request: https://github.com/gitgitgadget/git/pull/1022

Range-diff vs v1:

 -:  ----------- > 1:  2f566f330e0 test-lib-functions: use 'TEST_SHELL_PATH' in 'test_pause'
 1:  bf916ad98cc ! 2:  00211457ece test-lib-functions: use user's SHELL, HOME and TERM for 'test_pause'
     @@ Metadata
      Author: Philippe Blain <levraiphilippeblain@gmail.com>
      
       ## Commit message ##
     -    test-lib-functions: use user's SHELL, HOME and TERM for 'test_pause'
     +    test-lib-functions: optionally keep HOME, TERM and SHELL in 'test_pause'
      
          The 'test_pause' function, which is designed to help interactive
          debugging and exploration of tests, currently inherits the value of HOME
          and TERM set by 'test-lib.sh': HOME="$TRASH_DIRECTORY" and TERM=dumb. It
     -    also invokes the shell defined by SHELL_PATH, which defaults to /bin/sh.
     +    also invokes the shell defined by TEST_SHELL_PATH, which defaults to
     +    /bin/sh (through SHELL_PATH).
      
          Changing the value of HOME means that any customization configured in a
          developers' shell startup files and any Git aliases defined in their
     @@ Commit message
      
          To make the interactive command line experience in the shell invoked by
          'test_pause' more pleasant, save the values of HOME and TERM in
     -    USER_HOME and USER_TERM before changing them in test-lib.sh, and use
     -    these variables to invoke the shell in 'test_pause'. Also, invoke SHELL
     -    instead of SHELL_PATH, so that developer's interactive shell is used.
     +    USER_HOME and USER_TERM before changing them in test-lib.sh, and add
     +    options to 'test_pause' to optionally use these variables to invoke the
     +    shell. Also add an option to invoke SHELL instead of TEST_SHELL_PATH, so
     +    that developer's interactive shell is used.
     +
     +    We use options instead of changing the behaviour unconditionally since
     +    these three variables can break test reproducibility. Moreover, using the
     +    original HOME means tests could overwrite files in a user's home
     +    directory. Be explicit about these caveats in the new 'Usage' section in
     +    test-lib-functions.sh.
      
          Signed-off-by: Philippe Blain <levraiphilippeblain@gmail.com>
      
       ## t/test-lib-functions.sh ##
      @@ t/test-lib-functions.sh: test_tick () {
     + # Stop execution and start a shell. This is useful for debugging tests.
     + #
       # Be sure to remove all invocations of this command before submitting.
     ++#
     ++# Usage: test_pause [options]
     ++#   -t
     ++#	Use your original TERM instead of test-lib.sh's "dumb".
     ++#	This usually restores color output in the invoked shell.
     ++#	WARNING: this can break test reproducibility.
     ++#   -s
     ++#	Invoke $SHELL instead of $TEST_SHELL_PATH
     ++#	WARNING: this can break test reproducibility.
     ++#   -h
     ++#	Use your original HOME instead of test-lib.sh's "$TRASH_DIRECTORY".
     ++#	This allows you to use your regular shell environment and Git aliases.
     ++#	WARNING: this can break test reproducibility.
     ++#	CAUTION: this can overwrite files in your HOME.
       
       test_pause () {
     --	"$SHELL_PATH" <&6 >&5 2>&7
     -+	TERM="$USER_TERM" HOME="$USER_HOME" "$SHELL" <&6 >&5 2>&7
     +-	"$TEST_SHELL_PATH" <&6 >&5 2>&7
     ++	PAUSE_TERM=$TERM &&
     ++	PAUSE_SHELL=$TEST_SHELL_PATH &&
     ++	PAUSE_HOME=$HOME &&
     ++	while test $# != 0
     ++	do
     ++		case "$1" in
     ++		-t)
     ++			PAUSE_TERM="$USER_TERM"
     ++			;;
     ++		-s)
     ++			PAUSE_SHELL="$SHELL"
     ++			;;
     ++		-h)
     ++			PAUSE_HOME="$USER_HOME"
     ++			;;
     ++		*)
     ++			break
     ++			;;
     ++		esac
     ++		shift
     ++	done &&
     ++	TERM="$PAUSE_TERM" HOME="$PAUSE_HOME" "$PAUSE_SHELL" <&6 >&5 2>&7
       }
       
       # Wrap git with a debugger. Adding this to a command can make it easier
 2:  d51d0db6e25 < -:  ----------- test-lib-functions: use user's TERM and HOME for 'debug'
 -:  ----------- > 3:  1fac9baec1d test-lib-functions: optionally keep HOME and TERM in 'debug'