When configuring fails in Github Actions, print folded logs

A common, and challenging, issue in CI runners is debugging issues when
you know the information you want to check, but it's in the log file
which you don't have because remote CI machines.

There are various edge cases where this is especially hard to solve,
such as inside of `pip install` where the build directory with the log
file is automatically cleaned up. But it's never really *easy* when you
don't expect it, and the best case scenario is your iteration time gets
cut in half as you hurriedly go add some `cat`s to your CI scripts.

Meson can, at least sometimes, detect platforms where text can be
emitted inside of "folds", which are auto-collapsed and don't obscure
the general output, but when clicked will expand the logfile contents.
Hook this up.

We start off with a Github Actions implementation. We had some internal
code used by our own project tests runner, which can be utilized.

Also permit forcing it via an environment variable, in case
autodetection fails and you just want to force *something*, especially
when meson is called a couple layers deep inside some other tool.

1 files changed, 3 insertions, 0 deletions

diff --git a/mesonbuild/mesonmain.py b/mesonbuild/mesonmain.py
index c486dd846..faa0f426d 100644
--- a/mesonbuild/mesonmain.py
+++ b/mesonbuild/mesonmain.py
@@ -27,6 +27,9 @@ def errorhandler(e: Exception, command: str) -> int:
         logfile = mlog.shutdown()
         if logfile is not None:
             mlog.log("\nA full log can be found at", mlog.bold(logfile))
+            contents = mlog.ci_fold_file(logfile, f'CI platform detected, click here for {os.path.basename(logfile)} contents.')
+            if contents:
+                print(contents)
         if os.environ.get('MESON_FORCE_BACKTRACE'):
             raise e
         return 1