RoboFont: copy glif from git repo to layer in current glyph.

copyCurrentGitVersionToPrevLayer.py

"""
    
    Assuming you have
        a UFO open in RoboFont
        a current glyph selected
    and furthermore that
        this glyph is part of a git repository
        and that you have done some work on it
        and would like to compare the current state in robofont
            with the version in git
    then
        this script will get the .glif xml for the right file
        and write it to a layer named "prev"
        
    By running this script you agree that
        you understand that any data in the prev layer might be forfeit,
        you need to run the ufo3 version of robofab as you need the ufoLib,
    and that
        the author of this script is not responsible for any loss of data.
        

"""

import os
import subprocess
from ufoLib import UFOReader
from ufoLib.glifLib import readGlyphFromString
from defcon.objects.glyph import Glyph




f = CurrentFont()
g = CurrentGlyph()

cwd = os.getcwd()
if f is not None:
    targetPrev = g.getLayer('prev')
    targetPrev.clear()
    prevPen = targetPrev.getPointPen()
    reader = UFOReader(f.path)
    gs = reader.getGlyphSet()
    glifName = gs.contents.get(g.name)
    glyphsDir = os.path.join(f.path, "glyphs")
    if glifName is not None:
        path = os.path.join(glyphsDir, glifName)
        os.chdir(glyphsDir)
        cmd = "HEAD:./%s"%glifName
        p = subprocess.Popen(['git', 'show', cmd], stdout=subprocess.PIPE)
        glifXML = p.stdout.read()
        if len(glifXML)>0:
            readGlyphFromString(glifXML, targetPrev, prevPen)
            print "Updated %s from %s"%(g.name, glifName)
        else:
            print "No data found for %s"%g.name
            
os.chdir(cwd)

Update: check if we have any results before passing the xml to readGlyphFromString.