Add a page about package configuration locations

Author: lazka

mkdocs.yml

@@ -97,6 +97,7 @@ nav:
           - docs/package-management-tips.md
           - docs/package-management-faq.md
         - docs/filesystem-paths.md
+        - docs/configuration.md
         - Languages & Tools:
           - docs/cmake.md
           - docs/autotools.md

web/docs/configuration.md

@@ -0,0 +1,25 @@
+# Configuration Locations
+
+Cygwin packages, like openssh and git, follow the standard Unix conventions and
+use your `$HOME` or `$HOME/.config` directory for storing the user configuration
+and `/etc` for the system configuration.
+
+For native Windows programs the situation is a bit more complicated. For the
+user configuration some programs use the standard Windows paths, such as
+`%USERPROFILE%\AppData\Roaming`. In some cases native Windows programs are
+minimally ported from Unix and will write to `%USERPROFILE%\.appname` or
+`%USERPROFILE%\.config\appname`, or they will prefer the `HOME` environment
+variable over `USERPROFILE` and store their configuration in `$HOME\.appname` or
+`$HOME\.config\appname` like their Unix variants. For the system configuration
+some programs might store them alongside their other data files or in case they
+were ported from Unix they might follow the Unix layout and store things in
+`$MINGW_PREFIX/etc/appname`
+
+## FAQ
+
+**Can't all programs use the same location for their user configuration?**
+
+While having two locations for configuration can be confusing we want native
+programs to follow Windows conventions and be independent from MSYS2. Also we
+don't want to change the behavior of programs compared to their upstream
+versions unless we have to.