histedit: factored out diff/patch logic This patch is the first step towards a refactoring of the histedit extension to use underlying graft machinery instead of diff/patch as discussed in issue3527. Replacing diff/patch with graft is necessary to fix, for example, issue3582.

merge with stable

obsolete: import modules within mercurial/ without "from mercurial"

test-hybridencode: add cases for com0..9 and lpt0..9 note that com0 and lpt0 are *not* encoded