fix(diff): place --color flag before pathspec separator

[danny-kuehn]

Since #2905, PKGBUILD diffs lose color even with Color enabled in pacman.conf.

collectPkgbuildDiffs appends --color=always/never after the --
separator, so git treats it as a pathspec and ignores it. This predates
#2905 but was masked: Show() gave git a TTY, so auto color worked. With
Capture() git sees a pipe and disables color.

Fix: append the color flag before the range and pathspecs.

Tested: TZ=UTC make test, make lint, and manual diff review with color
on/off. Related: #2905, #1243.

[Jguer]

Awesome find @danny-kuehn , thanks for fixing this.

[radon-at-beeper]

Just for anyone else who finds this: the behavior still changes compared to before #1243, when diffs would be colorized under git config color.ui auto, even if Color was not enabled in pacman.conf. Now, it is required to enable Color in pacman.conf (just uncomment the line that says Color), if you want color in Yay diffs.

This is arguably more consistent, although it is surprising since the behavior changed, and some people might expect that configuring Git to color diffs would also apply to Git diffs within Yay.