Auto merge of #2600 - str4d:2497-hotfix-release, r=str4d

Implement process for hotfix releases

Closes #2497.

doc/hotfix-process.md

@@ -0,0 +1,74 @@
+Hotfix Release Process
+======================
+
+Hotfix releases are versioned by incrementing the build number of the latest
+release. For example:
+
+    First hotfix:  v1.0.11   -> v1.0.11-1
+    Second hotfix: v1.0.11-1 -> v1.0.11-2
+
+In the commands below, <RELEASE> and <RELEASE_PREV> are prefixed with a v, ie.
+v1.0.11 (not 1.0.11).
+
+## Create a hotfix branch
+
+Create a hotfix branch from the previous release tag, and push it to the main
+repository:
+
+    $ git branch hotfix-<RELEASE> <RELEASE_PREV>
+    $ git push 'git@github.com:zcash/zcash' hotfix-<RELEASE>
+
+## Implement hotfix changes
+
+Hotfix changes are implemented the same way as regular changes (developers work
+in separate branches per change, and push the branches to their own repositories),
+except that the branches are based on the hotfix branch instead of master:
+
+    $ git checkout hotfix-<RELEASE>
+    $ git checkout -b <BRANCH_NAME>
+
+## Merge hotfix PRs
+
+Hotfix PRs are created like regular PRs, except using the hotfix branch as the
+base instead of master. Each PR should be reviewed as normal, and then the
+following process should be used to merge:
+
+- A CI merge build is manually run by logging into the CI server, going to the
+  pr-merge builder, clicking the "force" button, and entering the following
+  values:
+
+  - Repository: https://github.com/<DevUser>/zcash
+    - <DevUser> must be in the set of "safe" users as-specified in the CI
+      config.
+  - Branch: name of the hotfix PR branch (not the hotfix release branch).
+
+- A link to the build and its result is manually added to the PR as a comment.
+
+- If the build was successful, the PR is merged via the GitHub button.
+
+## Release process
+
+The majority of this process is identical to the standard release process.
+However, there are a few notable differences:
+
+- When running the release script, use the `--hotfix` flag:
+
+    $ ./zcutil/make-release.py --hotfix <RELEASE> <RELEASE_PREV> <APPROX_RELEASE_HEIGHT>
+
+- To review the automated changes in git:
+
+    $ git log hotfix-<RELEASE>..HEAD
+
+- After the standard review process, use the hotfix merge process outlined above
+  instead of the regular merge process.
+
+- When making the tag, check out the hotfix branch instead of master.
+
+## Post-release
+
+Once the hotfix release has been created, a new PR should be opened for merging
+the hotfix release branch into master. This may require fixing merge conflicts
+(e.g. changing the version number in the hotfix branch to match master, if
+master is ahead). Such conflicts **MUST** be addressed with additional commits
+to the hotfix branch; specifically, the branch **MUST NOT** be rebased on
+master.

doc/release-process.md

@@ -2,6 +2,8 @@ Release Process
 ====================
 Meta: There should always be a single release engineer to disambiguate responsibility.
 
+If this is a hotfix release, please see `./hotfix-process.md` before proceeding.
+
 ## Pre-release
 
 ### Github Milestone
@@ -40,6 +42,11 @@ whole engineering team.
 
 ## Release process
 
+In the commands below, <RELEASE> and <RELEASE_PREV> are prefixed with a v, ie.
+v1.0.9 (not 1.0.9).
+
+### Create the release branch
+
 Run the release script, which will verify you are on the latest clean
 checkout of master, create a branch, then commit standard automated
 changes to that branch locally:

zcutil/make-release.py

@@ -27,6 +27,7 @@ def main(args=sys.argv[1:]):
             opts.RELEASE_VERSION,
             opts.RELEASE_PREV,
             opts.RELEASE_HEIGHT,
+            opts.HOTFIX,
         )
     except SystemExit as e:
         logging.error(str(e))
@@ -44,6 +45,12 @@ def parse_args(args):
         type=str,
         help='Path to repository root.',
     )
+    p.add_argument(
+        '--hotfix',
+        action='store_true',
+        dest='HOTFIX',
+        help='Use if this is a hotfix release from a non-master branch.',
+    )
     p.add_argument(
         'RELEASE_VERSION',
         type=Version.parse_arg,
@@ -63,9 +70,10 @@ def parse_args(args):
 
 
 # Top-level flow:
-def main_logged(release, releaseprev, releaseheight):
+def main_logged(release, releaseprev, releaseheight, hotfix):
     verify_releaseprev_tag(releaseprev)
-    initialize_git(release)
+    verify_version(release, releaseprev, hotfix)
+    initialize_git(release, hotfix)
     patch_version_in_files(release, releaseprev)
     patch_release_height(releaseheight)
     commit('Versioning changes for {}.'.format(release.novtext))
@@ -123,17 +131,41 @@ def verify_releaseprev_tag(releaseprev):
         )
 
 
+@phase('Checking version.')
+def verify_version(release, releaseprev, hotfix):
+    if not hotfix:
+        return
+
+    expected = Version(
+        releaseprev.major,
+        releaseprev.minor,
+        releaseprev.patch,
+        releaseprev.betarc,
+        releaseprev.hotfix + 1 if releaseprev.hotfix else 1,
+    )
+    if release != expected:
+        raise SystemExit(
+            "Expected {!r}, given {!r}".format(
+                expected, release,
+            ),
+        )
+
+
 @phase('Initializing git.')
-def initialize_git(release):
+def initialize_git(release, hotfix):
     junk = sh_out('git', 'status', '--porcelain')
     if junk.strip():
         raise SystemExit('There are uncommitted changes:\n' + junk)
 
     branch = sh_out('git', 'rev-parse', '--abbrev-ref', 'HEAD').strip()
-    if branch != 'master':
+    if hotfix:
+        expected = 'hotfix-' + release.vtext
+    else:
+        expected = 'master'
+    if branch != expected:
         raise SystemExit(
-            "Expected branch 'master', found branch {!r}".format(
-                branch,
+            "Expected branch {!r}, found branch {!r}".format(
+                expected, branch,
             ),
         )