log: add a "graphwidth" template variable Wrapping text in templates for 'hg log --graph' can't be done very well, because the template doesn't know how wide the graph drawing is. The edge drawing function needs to know the number of lines in the template output, so we need to also determine how wide that drawing would be before we call the edgefn or evaluate the template. This patch makes edgefn compute the graph width and pass it into the template so that we can do something like this: COLUMNS=10 hg log --graph --template "{fill(desc, termwidth - graphwidth)}" @ a a a a | a a a a | a a a a o a a a |\ a a a | | a a a | | a a a Using extensions to do this would be relatively complicated due to a lack of hooks in this area of the code. In the future it may make sense to have a more generic "textwidth" that tells you how many columns you can expect to fill without causing the terminal to wrap your output. I'm not sure there are other situations to motivate this yet, or if it is entirely feasible. Differential Revision: https://phab.mercurial-scm.org/D360