Support --color-moved

[mookid]

Currently, diffs obtained from git with the --color-moved flag parsed and re-highlighted completely, and the code move special highlighting is lost.

The color-moved information should be preserved.

[guettli]

It would be nice to see moved lines somehow. Maybe there is an alternative to --color-moved flag?

[mentalisttraceur]

In the meantime, it's possible to write a super hacky pager command that can combine diffr with --moved-lines, by first escaping lines in an unambiguous way that won't mess up the diff refinement, and then unescaping them back and adding the desired moved colors on the other end:

sed '
    s/^ / A/
    s/^\x1b\[1;35m-/ B/
    s/^\x1b\[1;36m+/ C/
    s/^\x1b\[1;34m-/ D/
    s/^\x1b\[1;33m+/ E/
' \
| diffr \
    --colors removed:none:background:0x50,0x00,0x00 \
    --colors added:none:background:0x00,0x50,0x00 \
    --colors refine-removed:none:background:0x80,0x00,0x00 \
    --colors refine-added:none:background:0x00,0x80,0x00 \
| sed '
    s/^\x1b\[0m A/ /
    s/^\x1b\[0m B/\x1b[48;2;64;0;64m-/
    s/^\x1b\[0m C/\x1b[48;2;0;64;64m+/
    s/^\x1b\[0m D/\x1b[48;2;80;48;80m-/
    s/^\x1b\[0m E/\x1b[48;2;48;80;80m+/
' \
| less -R

Attrocious. But it works:

1. Detect moved lines by their terminal color escape sequences (there are four moved colors, with Git's "zebra" option -- two removed-moved and two added-moved colors, which allows seeing the boundaries of adjacent moved chunks).
2. Replace the leading "-" and "+" from moved lines with a space, so that diffr ignores them as context.
3. But step 2 would create ambiguity with actual context lines, so all lines that already started with a space get prefixed with "A", and the four different moved colors get prefixed with "B"-"E".
4. Pipe through diffr.
5. Unescape, restoring the "-" and "+" prefixes for moved lines and adding the terminal escape sequences for desired moved line styling.

[mookid]

awesome!