use a Deployer for setting the remote git hash

- Revised DovecotDeployer to use _configure_remote_units() and
  _activate_remote_units() to deploy doveauth.  This keeps the
  Dovecot-related services in a single deployer class, leaving only
  services that are part of the chatmail project in
  ChatmailVenvDeployer.
- Removed doveauth from the unit list in ChatmailVenvDeployer.

ARCHITECTURE.md

@@ -1,4 +1,6 @@
-This diagram shows components of the chatmail server; this is a draft
+## Chatmail Relay
+
+This diagram shows components of the chatmail relay; this is a draft
 overview as of mid-August 2025:
 
 ```mermaid
@@ -48,3 +50,66 @@ graph LR;
 The edges in this graph should not be taken too literally; they
 reflect some sort of communication path or dependency relationship
 between components of the chatmail server.
+
+## cmdeploy
+
+cmdeploy is a Python program that uses the pyinfra library to deploy
+chatmail servers, with all the necessary software, configuration, and
+services.  The deployment process performs three primary types of operation:
+
+1. Installation of software, universal across all deployments.
+2. Configuration of software, with deploy-specific variations.
+3. Activation of services.
+
+The process is implemented through a family of "deployer" objects
+which all derive from a common `Deployer` base class, defined in
+[deployer.py](cmdeploy/src/cmdeploy/deployer.py).  Each object
+provides implementation methods for the three stages -- install,
+configure, and activate.  The top-level procedure in
+`deploy_chatmail()` calls these methods for all the deployer objects,
+first calling all the install methods, then the configure methods,
+then the activate methods.
+
+The base class also implements support for a CMDEPLOY_STAGES
+environment variable, which allows limiting the process to specific
+stages.  Note that some deployers are stateful between the stages
+(this is one reason why they are implemented as objects), and that
+state will not get propagated between stages when run in separate
+invocations of cmdeploy.  This environment variable is intended for
+use in future revisions to support building Docker images with
+software pre-installed, and configuration of containers at run time
+from environmnet variables.
+
+The `install_impl()` method for the deployer classes is static, to
+ensure that it does not rely on any object state, in particular, the
+configuration details of the deployment.  This helps ensure that all
+install methods are suitable for running as part of a container image
+build.
+
+Operations that start services for systemd-based deployments should
+only be called from the `activate_impl()` methods.  These methods will
+not be called in non-systemd container environments.
+
+### Deployer objects
+
+One might ask why the deployers are implemented as object classes, as
+opposed to callable functions or the like.  There are various reasons
+why objects are a good fit for the deployment process.
+
+1. Objects provide a way to organize the install, configure, and
+deploy operations for each component that is installed, supporting a
+"driver" type of pattern.  This could be implemented in other ways
+without objects, such as function jump tables, but objects provide a
+clean and formalized way to do essentially the same thing.
+
+2. Class inheritance provides a natural way to define
+component-specific operations for the various stages of deployment, by
+overriding the no-op stub methods in the base class.  The base class
+handles policy decisions about which stages are to be executed,
+ensuring consistent handling of the stages in a central location.
+
+3. Some of the components track state between stages, basing decisions
+like whether to restart a service on whether the software or
+configuration of that service was changed in an earlier stage.
+Keeping track of state between method calls is an ideal use case for
+objects.

CHANGELOG.md

@@ -2,6 +2,9 @@
 
 ## untagged
 
+- Organized cmdeploy into install, configure, and activate stages
+  ([#695](https://github.com/chatmail/relay/pull/695))
+
 - don't deploy the website if there are merge conflicts in the www folder
   ([#714](https://github.com/chatmail/relay/pull/714))
 

cmdeploy/src/cmdeploy/acmetool/__init__.py

@@ -2,66 +2,79 @@ import importlib.resources
 
 from pyinfra.operations import apt, files, server, systemd
 
+from ..deployer import Deployer
 
-def deploy_acmetool(email="", domains=[]):
-    """Deploy acmetool."""
-    apt.packages(
-        name="Install acmetool",
-        packages=["acmetool"],
-    )
 
-    files.put(
-        src=importlib.resources.files(__package__).joinpath("acmetool.cron").open("rb"),
-        dest="/etc/cron.d/acmetool",
-        user="root",
-        group="root",
-        mode="644",
-    )
+class AcmetoolDeployer(Deployer):
+    def __init__(self, *, email, domains, **kwargs):
+        super().__init__(**kwargs)
+        self.domains = domains
+        self.email = email
+        self.need_restart = False
 
-    files.put(
-        src=importlib.resources.files(__package__).joinpath("acmetool.hook").open("rb"),
-        dest="/usr/lib/acme/hooks/nginx",
-        user="root",
-        group="root",
-        mode="744",
-    )
+    @staticmethod
+    def install_impl():
+        apt.packages(
+            name="Install acmetool",
+            packages=["acmetool"],
+        )
 
-    files.template(
-        src=importlib.resources.files(__package__).joinpath("response-file.yaml.j2"),
-        dest="/var/lib/acme/conf/responses",
-        user="root",
-        group="root",
-        mode="644",
-        email=email,
-    )
+    def configure_impl(self):
+        files.put(
+            src=importlib.resources.files(__package__).joinpath("acmetool.cron").open("rb"),
+            dest="/etc/cron.d/acmetool",
+            user="root",
+            group="root",
+            mode="644",
+        )
 
-    files.template(
-        src=importlib.resources.files(__package__).joinpath("target.yaml.j2"),
-        dest="/var/lib/acme/conf/target",
-        user="root",
-        group="root",
-        mode="644",
-    )
+        files.put(
+            src=importlib.resources.files(__package__).joinpath("acmetool.hook").open("rb"),
+            dest="/usr/lib/acme/hooks/nginx",
+            user="root",
+            group="root",
+            mode="744",
+        )
 
-    service_file = files.put(
-        src=importlib.resources.files(__package__).joinpath(
-            "acmetool-redirector.service"
-        ),
-        dest="/etc/systemd/system/acmetool-redirector.service",
-        user="root",
-        group="root",
-        mode="644",
-    )
+        files.template(
+            src=importlib.resources.files(__package__).joinpath("response-file.yaml.j2"),
+            dest="/var/lib/acme/conf/responses",
+            user="root",
+            group="root",
+            mode="644",
+            email=self.email,
+        )
 
-    systemd.service(
-        name="Setup acmetool-redirector service",
-        service="acmetool-redirector.service",
-        running=True,
-        enabled=True,
-        restarted=service_file.changed,
-    )
+        files.template(
+            src=importlib.resources.files(__package__).joinpath("target.yaml.j2"),
+            dest="/var/lib/acme/conf/target",
+            user="root",
+            group="root",
+            mode="644",
+        )
 
-    server.shell(
-        name=f"Request certificate for: {', '.join(domains)}",
-        commands=[f"acmetool want --xlog.severity=debug {' '.join(domains)}"],
-    )
+        service_file = files.put(
+            src=importlib.resources.files(__package__).joinpath(
+                "acmetool-redirector.service"
+            ),
+            dest="/etc/systemd/system/acmetool-redirector.service",
+            user="root",
+            group="root",
+            mode="644",
+        )
+        self.need_restart = service_file.changed
+
+    def activate_impl(self):
+        systemd.service(
+            name="Setup acmetool-redirector service",
+            service="acmetool-redirector.service",
+            running=True,
+            enabled=True,
+            restarted=self.need_restart,
+        )
+        self.need_restart = False
+
+        server.shell(
+            name=f"Request certificate for: {', '.join(self.domains)}",
+            commands=[f"acmetool want --xlog.severity=debug {' '.join(self.domains)}"],
+        )

cmdeploy/src/cmdeploy/deployer.py

@@ -0,0 +1,59 @@
+import os
+
+from pyinfra.operations import server
+
+
+class Deployment:
+    def install(self, deployer):
+        # optional 'required_users' contains a list of (user, group, secondary-group-list) tuples.
+        # If the group is None, no group is created corresponding to that user.
+        # If the secondary group list is not None, all listed groups are created as well.
+        required_users = getattr(deployer, "required_users", [])
+        for user, group, groups in required_users:
+            if group is not None:
+                server.group(
+                    name="Create {} group".format(group), group=group, system=True
+                )
+            if groups is not None:
+                for group2 in groups:
+                    server.group(
+                        name="Create {} group".format(group2), group=group2, system=True
+                    )
+            server.user(
+                name="Create {} user".format(user),
+                user=user,
+                group=group,
+                groups=groups,
+                system=True,
+            )
+
+        ret = bool(deployer.install())
+        if ret:
+            deployer.need_restart = True
+
+    def configure(self, deployer):
+        deployer.configure()
+
+    def activate(self, deployer):
+        deployer.activate()
+
+    def perform_stages(self, deployers):
+        default_stages = "install,configure,activate"
+        stages = os.getenv("CMDEPLOY_STAGES", default_stages).split(",")
+
+        for stage in stages:
+            for deployer in deployers:
+                getattr(self, stage)(deployer)
+
+
+class Deployer:
+    need_restart = False
+
+    def install(self):
+        pass
+
+    def configure(self):
+        pass
+
+    def activate(self):
+        pass

cmdeploy/src/cmdeploy/policy-rc.d

@@ -0,0 +1,3 @@
+#!/bin/sh
+echo "All runlevel operations denied by policy" >&2
+exit 101