[PATCH v3] scalar: show progress if stderr refer to a terminal

From: ZheNing Hu <adlternative@gmail.com>

Sometimes when users use scalar to download a monorepo with a long commit history, they want to check the progress bar to know how long they still need to wait during the fetch process, but scalar suppresses this output by default.

So let's check whether scalar stderr refer to a terminal, if so, show progress, otherwise disable it.

Signed-off-by: ZheNing Hu <adlternative@gmail.com>
---
    scalar: show progress if stderr refer to a terminal
    
    When users use scalar to download a monorepo with a long commit history
    (or the client and server network communication is very poor), we often
    need to spend a long time in the fetch phase of scalar, some users may
    want to check this progress bar To understand the progress of fetch and
    how long they have to wait, so we should enable scalar to display fetch
    progress.
    
    v1. add [--verbose| -v] to scalar clone.
    
    v2.
    
     1. remove --verbose option.
     2. check if scalar stderr refer to terminal, if so, show progress.
    
    v3.
    
     1. fix some tests suggested by Derrick Stolee.
    
    Note: output look like this:
    
    $ scalar clone git@github.com:git/git.git
    Initialized empty Git repository in /home/adl/test/git/src/.git/
    remote: Enumerating objects: 208997, done.
    remote: Counting objects: 100% (870/870), done.
    remote: Compressing objects: 100% (870/870), done.
    remote: Total 208991 (delta 0), reused 870 (delta 0), pack-reused 208121
    remote: Enumerating objects: 470, done.
    remote: Counting objects: 100% (418/418), done.
    remote: Compressing objects: 100% (418/418), done.
    remote: Total 470 (delta 1), reused 0 (delta 0), pack-reused 52
    Receiving objects: 100% (470/470), 1.96 MiB | 1.64 MiB/s, done.
    Resolving deltas: 100% (1/1), done.
    Updating files: 100% (471/471), done.
    branch 'master' set up to track 'origin/master'.
    Switched to a new branch 'master'
    Your branch is up to date with 'origin/master'.
    
    
    "new branch", "new tag" output is a bit annoying, it would be better to
    suppress them, but keep the progress.

Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-1441%2Fadlternative%2Fzh%2Fscalar-verbosity-v3
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-1441/adlternative/zh/scalar-verbosity-v3
Pull-Request: https://github.com/gitgitgadget/git/pull/1441

Range-diff vs v2:

 1:  2e4c296bd19 ! 1:  38e7e0d44d1 scalar: show progress if stderr refer to a terminal
     @@ t/t9211-scalar-clone.sh: test_expect_success '--no-single-branch clones all bran
      +
      +	test_terminal env GIT_PROGRESS_DELAY=0 \
      +		scalar clone "file://$(pwd)/to-clone" "$enlistment" 2>stderr &&
     -+	grep --count "Enumerating objects" stderr >actual &&
     -+	echo 2 >expected &&
     -+	test_cmp expected actual &&
     ++	grep "Enumerating objects" stderr >actual &&
     ++	test_line_count = 2 actual &&
      +	cleanup_clone $enlistment
      +'
      +
     -+test_expect_success 'progress without tty' '
     ++test_expect_success TTY 'progress without tty' '
      +	enlistment=progress2 &&
      +
      +	test_config -C to-clone uploadpack.allowfilter true &&
      +	test_config -C to-clone uploadpack.allowanysha1inwant true &&
      +
     -+	scalar clone "file://$(pwd)/to-clone" "$enlistment" 2>stderr &&
     ++	GIT_PROGRESS_DELAY=0 scalar clone "file://$(pwd)/to-clone" "$enlistment" 2>stderr &&
      +	! grep "Enumerating objects" stderr &&
      +	! grep "Updating files" stderr &&
      +	cleanup_clone $enlistment
      +'
     ++
       test_done

 scalar.c                | 10 +++++++---
 t/t9211-scalar-clone.sh | 26 ++++++++++++++++++++++++++
 2 files changed, 33 insertions(+), 3 deletions(-)