wireprotov2: change how revisions are specified to changesetdata Right now, we have a handful of arguments for specifying the revisions whose data should be returned. Defining how all these arguments interact when various combinations are present is difficult. This commit establishes a new, generic mechanism for specifying revisions. Instead of a hodgepodge of arguments defining things, we have a list of dicts that specify revision selectors. The final set of revisions is a union of all these selectors. We implement support for specifying revisions based on: * An explicit list of changeset revisions * An explicit list of changeset revisions plus ancestry depth * A DAG range between changeset roots and heads If you squint hard enough, this problem has already been solved by revsets. But I'm reluctant to expose revsets to the wire protocol because that would require servers to implement a revset parser. Plus there are security and performance implications: the set of revision selectors needs to be narrowly and specifically tailored for what is appropriate to be executing on a server. Perhaps there would be a way for us to express the "parse tree" of a revset query, for example. I'm not sure. We can explore this space another time. For now, the new mechanism should bring sufficient flexibility while remaining relatively simple. The selector "types" are prefixed with "changeset" because I plan to add manifest and file-flavored selectors as well. This will enable us to e.g. select file revisions based on a range of changeset revisions. Differential Revision: https://phab.mercurial-scm.org/D4979

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  $ hg init a

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  $ cd a

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  $ hg diff inexistent1 inexistent2

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  inexistent1: * (glob)

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  inexistent2: * (glob)

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  $ echo bar > foo

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  $ hg add foo

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  $ hg ci -m 'add foo'

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  $ echo foobar > foo

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  $ hg ci -m 'change foo'

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  $ hg --quiet diff -r 0 -r 1

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  --- a/foo	Thu Jan 01 00:00:00 1970 +0000

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  +++ b/foo	Thu Jan 01 00:00:00 1970 +0000

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  @@ -1,1 +1,1 @@

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  -bar

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  +foobar

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  $ hg diff -r 0 -r 1

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  diff -r a99fb63adac3 -r 9b8568d3af2f foo

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  --- a/foo	Thu Jan 01 00:00:00 1970 +0000

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  +++ b/foo	Thu Jan 01 00:00:00 1970 +0000

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  @@ -1,1 +1,1 @@

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  -bar

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  +foobar

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  $ hg --verbose diff -r 0 -r 1

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  diff -r a99fb63adac3 -r 9b8568d3af2f foo

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  --- a/foo	Thu Jan 01 00:00:00 1970 +0000

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  +++ b/foo	Thu Jan 01 00:00:00 1970 +0000

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  @@ -1,1 +1,1 @@

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  -bar

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  +foobar

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  $ hg --debug diff -r 0 -r 1

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  diff -r a99fb63adac3f31816a22f665bc3b7a7655b30f4 -r 9b8568d3af2f1749445eef03aede868a6f39f210 foo

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  --- a/foo	Thu Jan 01 00:00:00 1970 +0000

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  +++ b/foo	Thu Jan 01 00:00:00 1970 +0000

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  @@ -1,1 +1,1 @@

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  -bar

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  +foobar

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  $ cd ..