help: document requirements We didn't have unified documentation of the various repository requirements. This patch changes that.

showstack: use absolute_import

contrib: use absolute_import in win32/hgwebdir_wsgi.py

dispatch: catch KeyboardInterrupt more broadly Because _runcatch() can run long operations in its exception handler, it wasn't enough to catch KeyboardInterrupt at the same level. For example, "hg unknown" will load all extension modules, so we could easily make it crashed by Ctrl-C.

histedit: have dropmissing abort on empty plan We noticed that many users have the intuition of laving the editor empty when they want to abort the operation. The fact that dropmissing allows user to delete all edited commits is not intuitive even for users that asked for it. Let's prevent people from this footgun.

streamclone: fix error when store files grow while stream cloning Effectively a backout of 9fea6b38a8da, but updated to using 'with'.

tests: add test of stream clone of repo that is changing This reveals an error introduced by 9fea6b38a8da.

chgserver: handle ParseError during validate Currently the validate command in chgserver expects config can be loaded without issues but the config can be broken and chg will print a stacktrace instead of the parsing error, if a chg server is already running. This patch adds a handler for ParseError in validate and a new instruction "exit" to make the client exit without abortmsg. A test is also added to make sure it will behave as expected.

dispatch: extract common logic for handling ParseError The way ParseError is handled at two different places in dispatch.py is the same. Move common logic into _formatparse.

chgserver: resolve relative path before sending via system channel The chgserver may have a different cwd from the client because of the side effect of "--cwd" and other possible os.chdir done by extensions. Therefore relative paths can be misunderstood by the client. This patch solves it by expanding relative cwd path to absolute one before sending them via the 'S' channel. It can help chg to pass a testcase in test-alias.t later.