contrib: PowerShell script to install development dependencies Configuring a Windows machine to hack on Mercurial is a bit of work and it isn't documented very well. This commit introduces a PowerShell script to automate going from a fresh Windows install to an environment suitable for building Mercurial, its installers, and running tests. Differential Revision: https://phab.mercurial-scm.org/D6141

chistedit: change in-progress message Saying "running histedit" is an artifact of when chistedit was a separate thing from histedit. I found the message a bit confusing, since wasn't I running histedit from the beginning, just from the curses interface? The whole thing is now histedit, both the curses interface and the underlying procedure to apply a plan, so let's use a message that doesn't make a distinction.

perf: copyedit a few documentation strings Differential Revision: https://phab.mercurial-scm.org/D6170

shelve: add --keep to list of allowables

perf: introduce a `perf.run-limits` options This options make it possible to configure the number of run that the extensions will perform. This is useful for automated benchmark or for performance measurement that need better accuracy.

perf: pass limits as a function argument The function applying the limit has no access to the configuration. Therefore, some higher layer will have to pass it as argument. We do this in an independent change to clarify the next change.

perf: more flexible implementation for checking stop conditions We want to make this logic simpler to configure. The first step is to stop hard-coding every values.

perf: document perfparents

perf: document config options We have configuration, so we better document it.

tests: use "perf" as a the extension name in test-contrib-perf.t This is simpler and seems more "inline" with the name people usually use for this extensions.