Automatically use pager for failed output

[mgaunard]

When compilation fails, the error message may be very long. I frequently pipe it to 'less' manually.
It would be nice if ninja, like git, could use the less pager automatically.

[sorbits]

Could make it use NINJA_PAGER if set, but not the default.

My terminal gives me better scrolling and searching than ‘less’ plus I often run ninja from a non-tty.

Also, ‘less’ has the issue that once you quit it, the output is gone.

[mgaunard]

It wouldn't use anything if the output is a non-tty.
I have no problem with defining a NINJA_PAGER environment variable otherwise.

Note that you can keep the output with 'less' by using the -X option. The -F option is also interesting as it will quit automatically if the whole output fits on one screen.
I believe git uses -FRSX by default.

[evmar]

I do like the way git's output works, but I'm not clear on how all this would interact with ninja printing status as it builds, particularly if you pass -k (keep going) and you're intermixing error output with status updates.

[mgaunard]

It should probably only be used for errors, and not when -k is enabled.