`tig blame` should accept absolute paths even when not run from repo root

[ilyagr]

After cloning tig repo into ~/dev, this works: cd ~/dev/tig; tig blame -- $(realpath src/tig.c).

However, the following does not work:

$ cd ~/dev/tig/src; tig blame -- $(realpath tig.c )
tig: No blame exist for src//Users/ilyagr/dev/tig/src/tig.c

I'd like it to work.

I checked this on a recent master, 025d2fb, on Darwin-arm.

The analogous Git command works. I haven't, at this point, looked into whether tig has an analogue of

https://github.com/git/git/blob/6ad802182101d622e6a4132f48292ddfa79e2024/setup.c#L153

The reason I noticed this bug is that I tried to invoke tig blame from a file manager, https://github.com/gokcehan/lf, which tends to use absolute paths (in the $fx environment variable it sets) while also often running the command from the same dir that the file was in.

[ilyagr]

Thank you!