tools/mkhtml.py: fix module/official addons source code and history URL branch

[tmszi]

Describe the bug
Module (compilation), official addon which is installed from the local directory have incorrect manual page source code and history URL, which URL path don't match GRASS GIS release branch name.

To Reproduce
Steps to reproduce the behavior:

Module:

1. Install GRASS GIS 7.8 release version
2. Check some module manual page source code and history URL e.g. v.surf.rst cat /usr/lib64/grass78/docs/html/v.surf.rst.html

<p>
<i>Last changed: $Date$</i>
--><h2>SOURCE CODE</h2>
<p>Available at: <a href="https://github.com/OSGeo/grass/tree/master/vector/v.surf.rst">v.surf.rst source code</a> (<a href="https://github.com/OSGeo/grass/commits/master/vector/v.surf.rst">history</a>)</p>
<hr class="header">
<p>

Addon:

1. Install GRASS 7.8 release version with this PR applied
2. Download some addon only e.g. g.extension -d wx.metadata
3. Install downloaded addon from the local directory g.extension wx.metadata url=/tmp/grass7-tomas-25558/tmpi9syivf2/wx.metadata
4. Check installed addon manual page source code and history URL e.g. g.gui.cswbrowser.html cat .grass7/addons/docs/html/g.gui.cswbrowser.html

Expected behavior
Module, official addon which is installed from the local directory should be have correct manual page source code and history URL which match GRASS GIS release.

System description:

• GRASS GIS version: releasebranch_7_8

[neteler]

Thanks, looks good!

[tmszi]

3ced08a rebase.

[tmszi]

@neteler I'm using in Python code f-string, which is available with version >= 3.6, but I can't find what is the minimum version of Python needed for GRASS GIS (7.8/8.0) to work.

[tmszi]

@neteler I'm using in Python code f-string, which is available with version >= 3.6, but I can't find what is the minimum version of Python needed for GRASS GIS (7.8/8.0) to work.

7.8 minimal Python version
8.0 minimal Python version

[neteler]

This is still subject to discussion: https://trac.osgeo.org/grass/wiki/RFC/8_LanguageStandardsSupportPython

I assume that Python 3.6+ is fine.