ui: add an uninterruptable context manager that can block SIGINT The blocking of SIGINT is not done by default, but my hope is that we will one day. This was inspired by Facebook's "nointerrupt" extension, which is a bit more heavy-handed than this (whole commands are treated as unsafe to interrupt). A future patch will enable this for varying bits of Mercurial that are performing unsafe operations. It's intentional that the KeyboardInterrupt is raised as the context manager exits: during the span of the context manager interrupting Mercurial could lead to data loss, but typically those spans are fairly narrow, so we can let the unsafe block complete and then terminate hg (which will leave the repo in a consistent state, even if it's not the user's desired state). .. api:: New context manager ``ui.uninterruptable()`` to mark portions of a command as potentially unsafe places to interrupt Mercurial with Control-C or similar. Differential Revision: https://phab.mercurial-scm.org/D3716