Handle less in a portable way

[Aankhen]

The current logic for special-casing less relies on the pager being specified as the literal string or using Unix-style paths. It also ignores the actual pager specified when calling it, so even if you set PAGER/BAT_PAGER to /my/path/to/less, bat will simply call less.

This PR treats any specified pager as a path and checks only the file stem so that C:\foo\bar\less.exe, /foo/bar/less, and less are all recognized. It also uses the specified less.

I managed to write a test for this by creating a stub bin/less.rs that verifies its arguments and the environment. However, this binary was installed along with bat when running cargo install. I haven’t yet found a way to test the behaviour without this issue, so for the moment I can only offer the fix without the test (but with the assurance that I’ve tested its behaviour both manually and automatically).

[sharkdp]

Fantastic stuff, thank you very much!

[sharkdp]

for the moment I can only offer the fix without the test (but with the assurance that I’ve tested its behaviour both manually and automatically).

Thank you for thinking about the tests! I'm fine with merging this without tests for now, as I still plan to extend our integration tests anyway.

[Aankhen]

Excellent!

[sharkdp]

Released in v0.7.0.