(deprecated, see 'hg help config.ui.editor')
(deprecated, see 'hg help config.ui.merge')
For each element in HGRCPATH:
In addition to the features disabled by "HGPLAIN=", the following values can be specified to adjust behavior:
Equivalent options set via command line flags or environment variables are not overridden.
See 'hg help scripting' for details.
Setting HGPLAINEXCEPT to anything (even an empty string) will enable plain mode.
(deprecated, see 'hg help config.ui.username')