Patch GAPDoc to allow out-of-tree compilation of manuals

[fingolfin]

Right now, the "make doc" target in the new build system always compiles the manual inside the GAP source directory, and not inside the build dir.

It would be nicer if we could run GAPDoc in such a way that it reads inputs from srcdir, but puts outputs below builddir. In other words: I want to run GAPDoc from srcdir/doc/ref, but instruct it to place all output files into builddir/doc/ref.

Perhaps this is already possible, but I could not figure out how (I did not try very hard, though).

BTW, I would also like to have this for my ReleaseTools, to build package manuals. For this, it would be also could if I could coax GAPDoc to produces the desired relative paths to the main GAP reference manual, even if this does not match the actual relative working directories... I.e. suppose GAP is in GAPROOT, and I want to generate manual files that work if placed in GAPROOT/pkg/foobar/doc (i.e. exactly what one wants for distribution). So normally GAPDoc would insert links to the GAP reference manual using ../../../doc/ref/ But I need to build the manual in /tmpdir/foobar/doc; and then GAPDoc currently will not create the correct relative links (at least I could not figure out a way to get it to do that).

So this goes a bit beyond the original application: I want GAPDoc to read inputs and write outputs to /tmpdir/foobar/doc, but create links as if those files were placed in GAPROOT/pkg/foobar/doc

[ChrisJefferson]

I would very much like something like this -- in general I feel much happier when I have directories with my files, and directories with auto-gen files, to make it easier to clean up!

[olexandr-konovalov]

I am sure Debian maintainers would appreciate this too.

[fingolfin]

We should also file a feature request for this at https://github.com/frankluebeck/GAPDoc/issues

[fingolfin]

I just had a look at this, it seems pretty easy to implement. I'll work on a pull request for GAPDoc.