commands: add debugdeltachain command We have debug commands for displaying overall revlog statistics (debugrevlog) and for dumping a revlog index (debugindex). As part of investigating various aspects of revlog behavior and performance, I found it important to have an understanding of how revlog delta chains behave in practice. This patch implements a "debugdeltachain" command. For each revision in a revlog, it dumps information about the delta chain. Which delta chain it is part of, length of the delta chain, distance since base revision, info about base revision, size of the delta chain, etc. The generic formatting facility is used, which means we can templatize output and get machine readable output like JSON. This command has already uncovered some weird history in mozilla-central I didn't know about. So I think it's valuable.

histedit: pick an appropriate base changeset by default (BC) Previously, `hg histedit` required a revision argument specifying which revision to use as the base for the current histedit operation. There was an undocumented and experimental "histedit.defaultrev" option that supported defining a single revision to be used if no argument is passed. Mercurial knows what changesets can be edited. And in most scenarios, people want to edit this history of everything on the current head that is rewritable. Making histedit do this by default and not require an explicit argument or additional configuration is a major usability win and will enable more people to use histedit. This patch changes the behavior of the experimental and undocumented "histedit.defaultrev" config option to select an appropriate base revision by default. Comprehensive tests exercising the edge cases in the new, somewhat complicated default revset have been added. Surprisingly, no tests broke. I guess we were never testing the behavior with no ANCESTOR argument (it used to fail with "abort: histedit requires exactly one ancestor revision"). The new behavior is much more user friendly. The functionality for choosing the default base revision has been moved to destutil.py, where it can easily be modified by extensions.

rebase: remove extra "if" from check of collapsing named branches

rebase: drop redundant functions to keep branch and graft source explicitly All entries in extra dict are propagated by default since 88fde8db5307.

color: drop useless override of ui.popbuffer() Because labels are applied at write() time since 717b75ae5bb0, colorui.popbuffer() is useless and it doesn't update _bufferapplylabels correctly. Removing it should fix the problem.

repoview: bypass changelog method to computed cache key Getting the data necessary for the cache key using the changelog/revlog method adds a significant overhead. Given how simple the underlying implementation is and often this code is ran, it makes sense to violate layering and directly compute the data. Testing `hg log` on Mozilla-central, this reduce the time spent on changelog cache validation by an extra half: before: 12.2s of 69s after: 6.1s of 62s Total speed up from this patch and it's parent is 3x (With stupid python profiler overhead) The global speedup without profiler overhead is still there, Before: 51s After: 39s (-23%)

repoview: stop recomputing cached key in all case As explained in the comment, we were computing the key of the cache value every time because of some obscure MQ test failure. I've dropped that code and ran the test again that failure is gone. I assume some transaction cleanup got rid of it. So we are dropping that code. This provide a significant speedup. Testing `hg log` on Mozilla-central this reduce the time spent on changelog cache validation by a third: before: 19.5s of 80s after: 12.2s of 69s (With stupid python profiler overhead)

commands.debugindexdot: use cmdutil.openrevlog() This pattern is used for all the other debug* commands that operate on revlogs. debugindexdot is an outlier. Make it conform.

commands: unify argument handling for revlog debug commands The same 3 options are used in a few locations and I'm about to add another. Might as well consolidate the pattern.

commit: fix rest syntax of examples This fixes the formatting of help/commit page and silence test-gendoc.t.

ui: optionally ignore sub-options from configitems() For convenience.

ui: add method to return option and all sub-options Apparently ":" has been blessed as a generic separator for options and sub-options. We formalize this by introducing an API for obtaining an option and all its sub-options. This will be used in a subsequent patch for declaring sub-options for [paths].

revlog: don't consider nullrev when choosing delta base In the most complex case, we try using the incoming delta base, then we try both parents, and then we try the previous revlog entry. If none of these result in a good delta, we natually use the null revision as base. However, we sometimes consider the nullrev before we have exhausted our other options. Specifically, when both parents are null, we use the nullrev as delta base if it produces a good delta (according to _isgooddelta()), and we fail to try the previous revlog entry as delta base. After 20a9226bdc8a (addrevision: use general delta when the incoming base delta is bad, 2015-12-01), it can also happen for non-merge commits when the incoming delta is not good. The Firefox repo (from many months back) shrinks a tiny bit with this patch: from 1.855GB to 1.830GB (1.4%). The hg repo itself shrinks even less: by less than 0.1%. There may be repos that get larger instead. This undoes the unexplained test change in 20a9226bdc8a.

revlog: make calls to _isgooddelta() consistent We always want to call _isgooddelta() before accepting a delta. We mostly call the function right after building the delta, but not always. Instead, we have an extra call at the end of the big code block. Let's make it consistent, so we call _isgooddelta() right after builddelta() and exactly once per delta. That also lets us rely on "delta is None" to mean we didn't find a good delta.

revlog: clarify which revision is added to 'tested' when using cached delta The tested delta revisions are added to the 'tested' set. These are the same revisions we pass to builddelta(). However, in one case, we add builddelta(rev)[3] to the set intead of adding 'rev' itself. In that particular case, that element is the same as the function's input revision (because self._generaldelta is true), so the effect is the same. Still, let's just add the function's input revision to avoid confusing future readers.

revlog: remove unused variable 'chainlen'

commit: adjust the quoting in the examples to be Windows friendly We should probably avoid strong quotes around command line args in the examples, since cmd.exe doesn't recognize them, and it will surprise a user who cargo cults them. I don't see a way to make a rule for this, since strong quoting is OK inside command line args, like within revsets.

wireproto: config options to disable bundle1 bundle2 is the new and preferred wire protocol format. For various reasons, server operators may wish to force clients to use it. One reason is performance. If a repository is stored in generaldelta, the server must recompute deltas in order to produce the bundle1 changegroup. This can be extremely expensive. For mozilla-central, bundle generation typically takes a few minutes. However, generating a non-gd bundle from a generaldelta encoded mozilla-central requires over 30 minutes of CPU! If a large repository like mozilla-central were encoded in generaldelta and non-gd clients connected, they could easily flood a server by cloning. This patch gives server operators config knobs to control whether bundle1 is allowed for push and pull operations. The default is to support legacy bundle1 clients, making this patch backwards compatible.

dockerlib: short form for non-unique uid/gid for CentOS 5 compat (issue4977) CentOS 5 does not support '--non-unique', but does support the short '-o'.

exchange: standalone function to determine if bundle2 is requested This will be used in a subsequent patch.

wireproto: add docstring for wirepeer

commit: add some help examples (issue4963) Includes documenting --date now, which resolves the above issue.

changegroup: restate file linknode callback using generator expressions I think this is slightly clearer, and it nicely avoids an extra nested function.

changegroup: clean up file lookup function One case is basically degenerate, so just extract it and make the function clearer.