This bugfix implements correct way to calculate source sha1 hash, before it will changed,
by propagation of unchanged sources.
This commit will also include regenerated static files and *.hash files.
Environment variables can contain a '=' in their value
KEY=BAR=1 sh -c 'echo KEY VALUE is "$KEY"'
If you just use Split() then you may not actually get a 'pair'
but rather a slice with length >= 3.
