Silence gen_contents_index for the common case.

The line: echo $HADDOCK_ARGS

From: https://github.com/ghc/ghc/blob/master/libraries/gen_contents_index#L53

Was introduced in: https://github.com/ghc/ghc/commit/2ad79aaa1b87164a0191e8f980f57a9fa0b80e0a

In archlinux (and other distros), gen_contents_index is run after installing a package using the distro's package manager to update the index file containing the list of libraries.

As a result of the commit, the output when installing a package can get very verbose.

Since the original intention of this change was to make it easier to debug crashes, I propose that there be a flag introduced into this script --verbose or --debug which would print out $HADDOCK_ARGS when specified so that the common case wouldn't include all the extra unneeded output.

I am willing to write a patch for this, if this idea is accepted.

Trac metadata

Trac field	Value
Version	7.4.1
Type	FeatureRequest
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Documentation
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