🐛 delta breaks git log

[neo-apz]

I'm experiencing an issue when running git log that causes the command to keep producing output and because there are many commits on my branch, the command just keeps printing. It seems no pagination is happening. Everything else works great and only this is causing an issue.

[dandavison]

Hi @neo-apz, delta tries to invoke a pager automatically. By default it tries to use less, but if you have an environment variable set such as PAGER= or PAGER=cat then you'd see the behaviour you describe. Can you post

• your OS
• which less
• env | grep -i pager

I'm converting this to a Discussion because it's not a bug or feature request.

[neo-apz]

Hi @dandavison,

Thanks for the prompt response.

Here are the things you asked for:

• My OS is Oracle Linux 7.
• Initially I was using the default less which was at /usr/bin/less and it was version 458 but when I saw this issue, I tried manually building the latest less from source (608) and now I'm using that which is at /usr/local/bin/less but even with that I have the same problem.
• This is empty (is it normal?)

[dandavison]

Hm. A few things you could try to shed light:

Do these page as expected?

git log | delta
git log | delta --paging=always
git log | delta --pager=$(which less)

These are slightly random tricks to check which less is being invoked by the git process:

GIT_PAGER='which less' git log
GIT_PAGER='less --version' git log

[neo-apz]

I tried all three git log commands and they all worked fine (I had disabled delta in my .gitconfig file before running them) and the two follow-up commands pointed to the latest less version that I installed (so /usr/local/bin/less and 608) was shown.

Then I re-enabled delta in my config file and reran things and now suddenly everything works fine and I have no idea how/why it's working fine now. 😄 🤷‍♂️

[dandavison]

OK cool! All's well that ends well.

[patrickhousley]

In case you are coming here because you are on MacOS and when you run git log, the log just disappears, use brew to update less.

OS: macOS 14.4.1 (23E224)

Before:

> less --version
less 581.2 (POSIX regular expressions)
Copyright (C) 1984-2021  Mark Nudelman

After:

> less --version
less 643 (PCRE2 regular expressions)
Copyright (C) 1984-2023  Mark Nudelman

[scarf005]

hi @neo-apz, sorry for bothering you. I'm getting the same issue from delta installed from distrobox. the pagination feature only works when i'm inside distrobox, and it doesn't work outside distrobox.

Reproduction

$ distrobox create --name fedora --image fedora
$ distrobox enter fedora
[distrobox] sudo dnf install git-delta
[distrobox] distrobox-export --bin $(which delta)
[distrobox] exit
$ which delta
/home/scarf/.local/bin/delta

Situation

GIT_PAGER=less git log

pagination works normally using less;

Do these page as expected?

git log | delta
git log | delta --paging=always
git log | delta --pager=$(which less)

all the three above only worked inside distrobox. it did not work outside distrobox.

These are slightly random tricks to check which less is being invoked by the git process:

GIT_PAGER='which less' git log
GIT_PAGER='less --version' git log

the output was same for both in and outside distrobox.

$ GIT_PAGER='which less' git log
/usr/bin/less
$ GIT_PAGER='less --version' git log
less 643 (POSIX regular expressions)
Copyright (C) 1984-2023  Mark Nudelman

less comes with NO WARRANTY, to the extent permitted by law.
For information about the terms of redistribution,
see the file named README in the less distribution.
Home page: https://greenwoodsoftware.com/less

System

• inside distrobox: fedora 40 (container image)
• outside distrobox: kinoite 40

[th1000s]

But plain git log and git log | less paginate correctly I assume? What less-specific env vars are set, can you check env | grep -i less? It might also be an issue with the terminal emulator, but usually less warns in this case, e.g. TERM=dumb git log

[scarf005]

But plain git log and git log | less paginate correctly I assume?

• git log without core.pager set works.
• git log with core.pagerset to delta no longer paginates.
• git log | less works.

What less-specific env vars are set, can you check env | grep -i less?

env | grep -i less
LESSOPEN=||/usr/bin/lesspipe.sh %s

It might also be an issue with the terminal emulator, but usually less warns in this case, e.g. TERM=dumb git log

• currently using konsole.
• TERM=dumb git log gives:

scarf@fedora /r/m/h/s/r/aoc-scala (main)> TERM=dumb git log
WARNING: terminal is not fully functional
Press RETURN to continue 

then regular less page with pagination.

[th1000s]

Can you strace the git and delta calls to less, writing it to a log file -o, including full syscall args and strings up to a length of 99 -v -s 99, following (process) forks -f, only looking at successful syscalls for process management -z -e process:

strace -o git.log -v -s 99 -f -z -e process git log -10 --patch # without the pager set

vs.

git log -10 --patch | strace -o delta.log -v -s 99 -f -z -e process delta

There should be an execve(..) call to less in both logs, but ignore the one with --version in delta. It has the arguments (those are interesting) and the env vars (do not post these, they might contain sensitive information), for example:

execve("/usr/bin/less", ["less", "--RAW-CONTROL-CHARS", "--quit-if-one-screen"], ["COLUMNS=165", "SECRET=01234", /* more env vars */ ]

delta will add LESSUTFCHARDEF, LESSCHARSET and LESSANSIENDCHARS env vars. Do you notice any difference in arguments or other env vars? Does setting the delta env vars in a shell before calling plain git log change the behavior?

[scarf005]

sorry, had little time, could only post logs.

scarf@fedora /r/m/h/s/r/aoc-scala (main)> PAGER='' strace -o git.log -v -s 99 -f -z -e process git log -10 --patch 2&> no-pager.log^C
scarf@fedora /r/m/h/s/r/aoc-scala (main)> git log -10 --patch | strace -o delta.log -v -s 99 -f -z -e process delta 2&> delta.log

no-pager.log
delta.log

p.s should this be converted into an issue as it's getting longer?

[scarf005]

related: 89luca89/distrobox#1572

[th1000s]

Well, the log is written to twice, only the strace output is interesting -o delta.log .. 2&> delta.log but that was overwritten (Luckily! There might be sensitive data in the env vars!).