discovery: prevent deleting items from a dictionary Removing elements from Python dictionary is expensive. So let's prevent adding them instead. I added a newline to make code look a bit better. Differential Revision: https://phab.mercurial-scm.org/D6146

discovery: drop some unused sets Differential Revision: https://phab.mercurial-scm.org/D6145

discovery: prevent recomputing info about server and outgoing changesets We already iterate over the outgoing.missing above and lookup repo for them. So let's reuse info calculated at that time instead of recomputing that again. Also we calculate the set of remotebranches by doing set(remotemap), so let's reuse that again. Upcoming patches will clean things a bit more. Differential Revision: https://phab.mercurial-scm.org/D6144

crecord: draw on the whole screen When starting crecord, one can see that it has a small gap on the rightmost column which doesn't get used. This is in contrast to other interactive curses frontends such as chistedit. Disabling the displaying of the cursor allows drawing on the whole availabe area and thus some hacky code in align() could be removed. Differential Revision: https://phab.mercurial-scm.org/D6171

automation: perform tasks on remote machines Sometimes you don't have access to a machine in order to do something. For example, you may not have access to a Windows machine required to build Windows binaries or run tests on that platform. This commit introduces a pile of code intended to help "automate" common tasks, like building release artifacts. In its current form, the automation code provides functionality for performing tasks on Windows EC2 instances. The hgautomation.aws module provides functionality for integrating with AWS. It manages EC2 resources such as IAM roles, EC2 security groups, AMIs, and instances. The hgautomation.windows module provides a higher-level interface for performing tasks on remote Windows machines. The hgautomation.cli module provides a command-line interface to these higher-level primitives. I attempted to structure Windows remote machine interaction around Windows Remoting / PowerShell. This is kinda/sorta like SSH + shell, but for Windows. In theory, most of the functionality is cloud provider agnostic, as we should be able to use any established WinRM connection to interact with a remote. In reality, we're tightly coupled to AWS at the moment because I didn't want to prematurely add abstractions for a 2nd cloud provider. (1 was hard enough to implement.) In the aws module is code for creating an image with a fully functional Mercurial development environment. It contains VC9, VC2017, msys, and other dependencies. The image is fully capable of building all the existing Mercurial release artifacts and running tests. There are a few things that don't work. For example, running Windows tests with Python 3. But building the Windows release artifacts does work. And that was an impetus for this work. (Although we don't yet support code signing.) Getting this functionality to work was extremely time consuming. It took hours debugging permissions failures and other wonky behavior due to PowerShell Remoting. (The permissions model for PowerShell is crazy and you brush up against all kinds of issues because of the user/privileges of the user running the PowerShell and the permissions of the PowerShell session itself.) The functionality around AWS resource management could use some improving. In theory we support shared tenancy via resource name prefixing. In reality, we don't offer a way to configure this. Speaking of AWS resource management, I thought about using a tool like Terraform to manage resources. But at our scale, writing a few dozen lines of code to manage resources seemed acceptable. Maybe we should reconsider this if things grow out of control. Time will tell. Currently, emphasis is placed on Windows. But I only started there because it was likely to be the most difficult to implement. It should be relatively trivial to automate tasks on remote Linux machines. In fact, I have a ~1 year old script to run tests on a remote EC2 instance. I will likely be porting that to this new "framework" in the near future. # no-check-commit because foo_bar functions Differential Revision: https://phab.mercurial-scm.org/D6142

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