log: rewrite default template to use labels (issue2866) This is a complete rewrite of the default template to use labels. This seems ultimately useless to me in most cases. The biggest benefit of this patch to me seems to be a fairly complicated example of the templating engine. It was a lot of hard work to figure out the precise acceptable syntax, since it's almost undocumented. Hat tip to Steve Losh's smartlog template, which helped me figure out a lot of the syntax. Hopefully later I can use the present default log template as an example for documenting the templating engine. A test is attached. My goal was to match the --color=debug output, which may differ slightly in newlines from the actual ANSI escape codes output. I consider this an acceptable invisible deviation. There seems to be a considerable slowdown with this rewrite. Before: $ time hg log -T default -r .~100::. > /dev/null real 0m0.882s user 0m0.812s sys 0m0.064s $ time hg log -T default -r .~100::. > /dev/null real 0m0.872s user 0m0.796s sys 0m0.068s $ time hg log -T default -r .~100::. > /dev/null real 0m0.917s user 0m0.836s sys 0m0.076s After: $ time hg log -T default -r .~100::. > /dev/null real 0m1.480s user 0m1.392s sys 0m0.072s $ time hg log -T default -r .~100::. > /dev/null real 0m1.500s user 0m1.400s sys 0m0.088s $ time hg log -T default -r .~100::. > /dev/null real 0m1.462s user 0m1.364s sys 0m0.092s Following the maxim, "make it work, profile, make it faster, in that order", I deem this slowdown acceptable for now. I suspect but have not confirmed that a big slowdown comes from calling keywords twice in the file templates, once to test the existence of output and again to actually list the output. If so, a simple speedup might be to improve the templating engine to cache keywords when called more than once on the same revision. TODO: I found a bug while working on this. The following stack traces: hg log -r . -T '{ifcontains(phase, "secret public", "lol", "omg")}\n'