sage-progress-meter (for builds silenced with make V=0)

[mkoeppe]

#21539 added support for make V=0 to silence the build.
This helps, for example, with Travis CI builds, which have a limit on the allowed output.

However, with some long-running spkg builds (such as gcc) it could be nice to have some indication of progress (for example, with a Travis CI build, to avoid the 10-minute-no-output kill).

This could be done by calling something like pv (the Pipe Viewer) in sage-logger. We can implement what we need in a few lines of basic Python, no need to add a pv dependency (note, for example, the Ubuntu pv package is not whitelisted for Travis CI container-based builds).

The opportunities for bikeshedding are endless on this one. I have a first implementation that just reads lines from stdin and discards them and checks the elapsed time; prints a 'still here' message to stderr every 5 minutes. (Good enough for a Travis CI build.) But could add:

• an optional prefix such as [gcc-4.3.4]
• progress indication, measured by output number of lines divided by expected number of lines
• watching for regex that indicate progress milestones (e.g., Comparing stages 2 and 3)

CC: @vbraun @jdemeyer @jhpalmieri @embray

Component: build

Author: Matthias Koeppe

Branch/Commit: u/mkoeppe/develop-travis-squashed @ c75a24d

Issue created by migration from https://trac.sagemath.org/ticket/21724

[mkoeppe]

Branch: u/mkoeppe/develop-travis-squashed

[embray]

Commit: c75a24d

[embray]

comment:2

This seems to be combining several things.... Since when are we trying to build Sage on Travis?

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New commits:

c75a24d

Add Travis scripts, sage-progress-meter

[mkoeppe]

comment:3

Yes, it's combining it with some experimental Travis build scripts, because this was my main use case for the progress meter. The ticket is not ready for review.