Re: [PATCH v4 1/2] gitk: write only changed configuration variables

> When gitk contains some changed parameter, and there is existing
> instance of gitk where the parameter is still old, it is reverted to
> that old value when the instance exits.
> 
> Instead, store a parameter in config only it is has been modified in the
> exiting instance. Otherwise, preserve the value which currently is in
> file.  This allows editing the configuration when several instances are
> running, and don't get rollback of the modification if some other
> instance where the configuration was not edited is closed last.
> 
> For scalar variables, use trace(3tcl) to detect their change. Since `trace` can
> send bogus events, doublecheck if the value has really been changed, but once
> it is marked as changed, do not reset it back to unchanged ever, because if
> user has restored the original value, it's the decision which should be stored
> as well as modified value.
> 
> Treat view list especially: instead of rewriting the whole list, merge
> individual views. Place old and updated views at their older placed, add
> new ones to the end of list. Collect modified view explicitly, in newviewok{}
> and delview{}.
> 
> Do not merge geometry values. They are almost always changing because
> user moves and resises windows, and there is no way to find which one of
> the geometries is most desired. Just overwrite them unconditionally,
> like earlier.
> 
> Signed-off-by: Max Kirillov <max@max630.net>