phabricator: add --amend option to phabsend Previously `hg phabsend` was imitating `hg email` and won't mutate changesets. That works fine with reviewer-push workflow, reviewers run `phabread`, `import`. However, it does not work well with author-push workflow. Namely, the author needs to run extra commands to get the right commit message, and remove the local tag after push. This patch solves those issues by adding the `--amend` option, so local changesets will have the right commit message, and tags become unnecessary. Test Plan: Given the following DAG: o 17 o 16 | o 15 | @ 14 |/ o 13 o 12 Run `hg phabsend '(13::)-17' --amend`, check the new DAG looks like: o 21 | o 20 | @ 19 |/ o 18 | o 17 | x 16 | x 13 |/ o 12 And commit messages are updated to contain the `Differential Revision` lines. Use `phabread` to make sure Phabricator has the amended node recorded. Also check `phabsend .` followed by a `phabsend . --amend`, the commit message will be updated and the tag will be removed. Differential Revision: https://phab.mercurial-scm.org/D122