Support for line range minus syntax

[bojan88]

Continuation from #1810

In case we are working with a long file and we are interested in line 55478, currently we could use 55478:+5 to quickly see 5 lines after 55478.

We might be interested to see a few lines preceding line 55478, and with this change we could do it with 55478:-5 or 55478:-30

This is influenced by similar syntax in git for log sub-command with -L argument.

[sharkdp]

This is influenced by similar syntax in git for log sub-command with -L argument.

Could you please explain to us if the syntax is only similar or exactly the same? Might make sense to adopt what git log implemented.

[bojan88]

This is influenced by similar syntax in git for log sub-command with -L argument.

Could you please explain to us if the syntax is only similar or exactly the same? Might make sense to adopt what git log implemented.

It's similar - git log -L has more options. Here's part of the description from man page:

-L<start>,<end>:<file>, -L:<funcname>:<file>

<start> and <end> can take one of these forms:

           •   number

               If <start> or <end> is a number, it specifies an
               absolute line number (lines count from 1).

           •   /regex/

               This form will use the first line matching the given
               POSIX regex. If <start> is a regex, it will search
               from the end of the previous -L range, if any,
               otherwise from the start of file. If <start> is
               ^/regex/, it will search from the start of file. If
               <end> is a regex, it will search starting at the line
               given by <start>.

           •   +offset or -offset

               This is only valid for <end> and will specify a
               number of lines before or after the line given by
               <start>.

[sharkdp]

Wait. Shouldn't that be 1? Is 0 a valid line number?

[bojan88]

Turns out it is.
Try running bat -r 0:5 [some_file] and bat -r 1:5 [some_file] - both commands produce the same output

[sharkdp]

Thank you for the updates!

Could you please add an entry to the "unreleased" section in CHANGELOG.md? The format for entries is:

- Description what has been changed, see #123 (@user)

where #123 links to the bug ticket and/or the PR and user is your username.

[bojan88]

@sharkdp updated. I also merged latest master.