docs: change `unstable` references to `orphan` Per https://www.mercurial-scm.org/wiki/CEDVocabulary

doc: correct a typo

docs: change `troubles` references to `instability` Per https://www.mercurial-scm.org/wiki/CEDVocabulary. There are a couple instances of 'troublesome' which probably need a word, as deriviatives of 'instability' didn't really fit. At least some of these are in the unlinked obs-terms.rst page.

docs: change `precursors` references to `predecessors` Per https://www.mercurial-scm.org/wiki/CEDVocabulary

docs: import figure diagrams with inkscape 0.92 No changes to the content here. This simply accepts the default option ("This file contains digital artwork for screen display") on the prompt when first opened, which is trying to upgrade from 90DPI to 96DPI.

messages: standardize on "working copy is now at" including "is" It seemed that we mostly used "is", but `hg next` and `hg prune` could print it without the "is".

evolve: move more of the progress-related variables together

evolve: delete dead calculation of number of troubled revisions The "count" variable is recalculated in the regular (no --continue) code path and it isn't used anywhere else (it used to be set to 1 in the --continue code path, but that now has its own progress counting).

evolve: drop nested locks and transactions All callers of _solveone() now take the locks and start the transactions, so there's no need to do that anymore.

next: start transaction before calling _solveone() All other callers do this, and I'm about to make _solveone() not create a transaction.

evolve: use single transaction also when continuing

evolve: run in a single transaction This speeds up `hg evolve --all` of a stack of 24 commits in the hg repo from 11.5s to 3.7s (3x). As can be seen in the tests, it also avoid some warnings about transiently unstable commits.

evolve: extract function for solving one revision, including merges Will make the next patch simpler.

evolve: mention that --all is the default behavior now

evolve: mention that not all successful operations currently update wdir

evolve: add progress support for --continue The progress starts where it left off when the previous command ran into merge conflicts.

evolve: reduce scope of progress-related variables

evolve: move progress-clearing out of _cleanup() The progress is only used with --all or --rev, so there's no need to clean it in any other case. It's therefore easier to clean it specifically in that case.

evolve: stop passing no-op "progresscb" into continueevolve() The "progresscb" doesn't do anything in the --continue case, so there's no need to pass it into continueevolve(). This lets us remove the --no-all that was added to the test as a workaround.

evolve: _solveunstable() update progress only once There's no need to draw it, then possibly write text over it (with --verbose), and then draw it again.

evolve: don't update progress just before clearing it _cleanup() will clear the progress, so there's little reason to update it just before (except for progress.debug=yes).

evolve: clean up progress bar also when using -r It looks like 1fe3da0b4601 (evolve: add --rev option to the evolve command, 2015-05-05) forgot to update the "showprogress" variable.

tests: add some basic testing of progress

evolve: increment progress *after* a whole merge commit is done The "re-stabilize" step was using the progress that was supposed to be for the next revision.

evolve: use util.acceptintervention() for closing transactions util.acceptintervention() will close the transaction on InterventionRequired.

evolve: use context manager for transactions

evolve: use consistent message and just re-raise InterventionRequired

evolve: use standard InterventionRequired instead of MergeFailure