diff mode doesn't display content

[sudoforge]

Describe the bug you encountered:

After installing bat for the first time, I wanted to test it out in my git repository. Running bat -d <filename> with a file that has been stored in my git repository's index and has a local modification does not output any of the content, modification or not.

➜ git d -- dotfiles/git/.config/git/config
diff --git a/dotfiles/git/.config/git/config b/dotfiles/git/.config/git/config
index 3eb29fd..75bdf05 100644
--- a/dotfiles/git/.config/git/config
+++ b/dotfiles/git/.config/git/config
@@ -23,6 +23,8 @@
   default = simple
 [pull]
   rebase = true
+[log]
+  mailmap = true
 [merge]
   ff = false
   tool = vimdiff


➜ bat -d dotfiles/git/.config/git/config
───────┬────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────
       │ File: dotfiles/git/.config/git/config
───────┼────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────
───────┴────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────

I am able to replicate this erroneous behavior in a new repository:

➜ mkdir /tmp/bat-diff-issue && cd /tmp/bat-diff-issue


➜ git init
Initialized empty Git repository in /tmp/bat-diff-issue/.git/


➜ echo "foo" > README


➜ git add -A && git commit -m 'initial commit'
[trunk (root-commit) 8e32fca] initial commit
 1 file changed, 1 insertion(+)
 create mode 100644 README


➜ echo "bar" > README


➜ git diff -- README
diff --git a/README b/README
index 257cc56..5716ca5 100644
--- a/README
+++ b/README
@@ -1 +1 @@
-foo
+bar


➜ bat -d README
───────┬────────────────────────────────────────────────────────────────────────────────────────────────────────────────
       │ File: README
───────┼────────────────────────────────────────────────────────────────────────────────────────────────────────────────
───────┴────────────────────────────────────────────────────────────────────────────────────────────────────────────────

What did you expect to happen instead?

I expected to see the modified line(s) with proper highlighting.

How did you install bat?

Through my system package manager.

➜ pacman -Qi bat | head -n5
Name            : bat
Version         : 0.18.3-1
Description     : Cat clone with syntax highlighting and git integration
Architecture    : x86_64
URL             : https://github.com/sharkdp/bat

---

bat version and environment

Software version

bat 0.18.3 (b146958)

Operating system

Linux 5.14.8-arch1-1

Command-line

bat -d --diagnostic README

Environment variables

SHELL=/usr/bin/zsh
PAGER=<not set>
LESS=<not set>
BAT_PAGER=<not set>
BAT_CACHE_PATH=<not set>
BAT_CONFIG_PATH=<not set>
BAT_OPTS=<not set>
BAT_STYLE=<not set>
BAT_TABS=<not set>
BAT_THEME=<not set>
XDG_CONFIG_HOME=/home/sudoforge/.config
XDG_CACHE_HOME=<not set>
COLORTERM=truecolor
NO_COLOR=<not set>
MANPAGER='nvim +Man'\!''

Config file

Compile time information

• Profile: release
• Target triple: x86_64-unknown-linux-gnu
• Family: unix
• OS: linux
• Architecture: x86_64
• Pointer width: 64
• Endian: little
• CPU features: fxsr,sse,sse2
• Host: x86_64-unknown-linux-gnu

Less version

> less --version
less 590 (PCRE2 regular expressions)
Copyright (C) 1984-2021  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

[sudoforge]

What's curious here is that LESS is detected as "not set" when running bat -d --diagnostic README:

➜ echo $LESS
-XFRi

However, upon testing, unsetting this has no effect whatsoever.

[eth-p]

Thanks for reporting this bug and providing instructions to reproduce it! It definitely looks like something's off with bat's output.

Some other bugged cases:

$ printf "foo\nbar" > README && git add README && git commit -m 'commit'
$ printf "baz\nbar" > README
$ bat -d README
───────┬─────────────────────────────────────────────────────────────────────────────────────────
       │ File: README
───────┼─────────────────────────────────────────────────────────────────────────────────────────
───────┴────────────────────────────────────────────────────────────────────────────────────────

$ printf "1\n2\n3" > README && git add README && git commit -m 'commit'
$ printf "0\n2\n3" > README
$ bat -d README
───────┬─────────────────────────────────────────────────────────────────────────────────────────
       │ File: README
───────┼─────────────────────────────────────────────────────────────────────────────────────────
───────┴────────────────────────────────────────────────────────────────────────────────────────

It looks like bat doesn't detect when the first line is changed.

[sudoforge]

It looks like bat doesn't detect when the first line is changed.

Just to be explicit here, this issue is present even when lines other than the first are modified.

[sharkdp]

Thank you for reporting this.

It looks like bat doesn't detect when the first line is changed.

Just to be explicit here, this issue is present even when lines other than the first are modified.

I can only reproduce the bug for the first line modification:

test.sh

seq 5 > README
git commit -am "dummy commit" > /dev/null

for i in $(seq 5); do
    echo "=== $i"
    sed -i -e "s/^$i\$/this line has been modified/" README
    bat --diff README
    git checkout README > /dev/null
done

output:

▶ bash test.sh
=== 1
───────┬─────────────────────────────────────────────
       │ File: README
───────┼─────────────────────────────────────────────
───────┴─────────────────────────────────────────────
=== 2
───────┬─────────────────────────────────────────────
       │ File: README
───────┼─────────────────────────────────────────────
   1   │ 1
   2 ~ │ this line has been modified
   3   │ 3
   4   │ 4
───────┴─────────────────────────────────────────────
=== 3
───────┬─────────────────────────────────────────────
       │ File: README
───────┼─────────────────────────────────────────────
   1   │ 1
   2   │ 2
   3 ~ │ this line has been modified
   4   │ 4
   5   │ 5
───────┴─────────────────────────────────────────────
=== 4
───────┬─────────────────────────────────────────────
       │ File: README
───────┼─────────────────────────────────────────────
   2   │ 2
   3   │ 3
   4 ~ │ this line has been modified
   5   │ 5
───────┴─────────────────────────────────────────────
=== 5
───────┬─────────────────────────────────────────────
       │ File: README
───────┼─────────────────────────────────────────────
   3   │ 3
   4   │ 4
   5 ~ │ this line has been modified
───────┴─────────────────────────────────────────────

[sudoforge]

Interestingly, I copied a file that I experience the issue with into a temporary "test" repository, and cannot reproduce the error there. I'll dig into bat --diff when I get a chance over the next week and try to pinpoint why we'd be seeing different behavior.