strange behavior with nonexistant or partially populated ~/.config/git/gitk

If ~/.config/git/gitk doesn't exist, I get small fonts (fine) and ugly hard-to-read dark green branch labels.

The fix for the dark green problem is here:

     http://stackoverflow.com/questions/26025810/gtk-apps-show-green-too-dark

But after doing:

      echo 'set headbgcolor lime' >~/.config/git/gitk ; gitk

I end up with a much more extensive ~/.config/git/gitk that changes fonts, window geometry, etc. to be different than the defaults that you get if you don't have ~/.config/git/gik. This is weird.

It should work one of these ways:

     1.  Any setting in ~/.config/git/gitk override the defaults, but
the file is not required, and running gitk doesn't create it or change
with it's contents.

     2.  ~/.config/git/gitk is always created if it doesn't exist or
isn't fully populated, and it gets the default values for anything not
defined.

The full ~/.config/git/gitk that gets created for me is below. I don't know where the setting that get used if it doesn't exist come from.

set mainfont {sans 9} set textfont {monospace 9} set uifont {sans 9 bold} set tabstop 8 set findmergefiles 0 set maxgraphpct 50 set maxwidth 16 set cmitmode patch set wrapcomment none set autoselect 1 set autosellen 40 set showneartags 1 set maxrefs 20 set visiblerefs {"master"} set hideremotes 0 set showlocalchanges 1 set datetimeformat {%Y-%m-%d %H:%M:%S} set limitdiffs 1 set uicolor grey85 set want_ttk 1 set bgcolor white set fgcolor black set uifgcolor black set uifgdisabledcolor #999 set colors {lime red blue magenta darkgrey brown orange} set diffcolors {red "#00a000" blue} set mergecolors {red blue lime purple brown "#009090" magenta "#808000" "#009000" "#ff0080" cyan "#b07070" "#70b0f0" "#70f0b0" "#f0b070" "#ff70b0"} set markbgcolor #e0e0ff set diffcontext 3 set selectbgcolor gray85 set foundbgcolor yellow set currentsearchhitbgcolor orange set extdifftool meld set perfile_attrs 0 set headbgcolor lime set headfgcolor black set headoutlinecolor black set remotebgcolor #ffddaa set tagbgcolor yellow set tagfgcolor black set tagoutlinecolor black set reflinecolor black set filesepbgcolor #aaaaaa set filesepfgcolor black set linehoverbgcolor #ffff80 set linehoverfgcolor black set linehoveroutlinecolor black set mainheadcirclecolor yellow set workingfilescirclecolor red set indexcirclecolor lime set circlecolors {white blue gray blue blue} set linkfgcolor blue set circleoutlinecolor black set geometry(main) 1837x989+5+53 set geometry(state) normal set geometry(topwidth) 1837 set geometry(topheight) 300 set geometry(pwsash0) "680 1" set geometry(pwsash1) "1020 1" set geometry(botwidth) 850 set geometry(botheight) 684 set permviews {}