context: switch ctx() use to changectx() I added `ctx()` to `overlayworkingfilectx`, (and before that, `absentfilectx`), because `absentfilectx` had reference to this function in its `cmp()` function. But the standard is actually `changectx()`, and no other class implements `ctx()`. So let's use the standard name. (As a result, I'm not sure that part of the `absentfilectx` comparator ever worked! It was written before I added either function.) This will be necessary in the next patch. Differential Revision: https://phab.mercurial-scm.org/D1211

lfs: introduce a user level cache for lfs files This is the same mechanism in place for largefiles, and solves several problems working with multiple local repositories. The existing largefiles method is reused in place, because I suspect that there are other functions that can be shared. If we wait a bit to identify more before `hg cp lfutil.py ...`, the history will be easier to trace. The push between repo14 and repo15 in test-lfs.t arguably shouldn't be uploading any files with a local push. Maybe we can revisit that when `hg push` without 'lfs.url' can upload files to the push destination. Then it would be consistent for blobs in a local push to be linked to the local destination's cache. The cache property is added to run-tests.py, the same as the largefiles property, so that test generated files don't pollute the real location. Having files available locally broke a couple existing lfs-test-server tests, so the cache is cleared in a few places to force file download.

largefiles: refactor _usercachedir() to allow reuse with lfs Largefiles puts everything into a flat directory, while lfs divides files up by creating subdirectories consisting of the first two characters of the hash. Therefore, pointing at the largefiles cache won't work.

lfs-test: note a problem with unpushed lfs files and cloning/sharing AFAIK, this isn't an issue with largefiles because it knows how to look in the system-wide cache.

patch: add within-line color diff capacity The `diff' command usually writes deletion in red and insertions in green. This patch adds within-line colors, to highlight which part of the lines differ. Lines to compare are decided based on their similarity ratio, as computed by difflib SequenceMatcher, with an arbitrary threshold (0.7) to decide at which point two lines are considered entirely different (therefore no inline-diff required). The current implementation is kept behind an experimental flag in order to test the effect on performance. In order to activate it, set inline-color-diff to true in [experimental].

dagop: extend filectxancestors() to walk multiple files