From 4a391609e8432782f3911464d303b2a62c7b6c2c Mon Sep 17 00:00:00 2001
From: Daniel Schadt <kingdread@gmx.de>
Date: Thu, 29 Sep 2022 20:53:27 +0200
Subject: fietsupdtr: noop if the update is already applied

---
 fietsboek/updater/__init__.py | 24 ++++++++++++++++++++++++
 fietsboek/updater/cli.py      | 22 ++++++++++++++++++----
 2 files changed, 42 insertions(+), 4 deletions(-)

diff --git a/fietsboek/updater/__init__.py b/fietsboek/updater/__init__.py
index 724defa..1c26715 100644
--- a/fietsboek/updater/__init__.py
+++ b/fietsboek/updater/__init__.py
@@ -258,6 +258,30 @@ class Updater:
         """
         return [rev_id for (rev_id, deps) in self.backward_dependencies.items() if not deps]
 
+    def has_applied(self, revision_id, backward=False):
+        """Checks whether the given revision is applied.
+
+        By default, this checks if a given update is applied, i.e. the current
+        version is greater-or-equal to the given revision ID. If ``backward``
+        is ``True``, we instead check if the current version is lower-or-equal
+        to the given revision ID.
+
+        Note that this function does not raise an error if the given revision
+        ID cannot be found and instead simply returns ``False``. Use
+        :meth:`exists` to check whether the revision actually exists.
+
+        :param revision_id: The revision to check.
+        :type revision_id: str
+        :param backward: Whether to switch the comparison direction.
+        :type backward: bool
+        :return: ``True`` if the current version at least matches the asked
+            revision ID.
+        :rtype: bool
+        """
+        if not backward:
+            return revision_id in self._transitive_versions()
+        return revision_id in self._reverse_versions() | set(self.current_versions())
+
 
 class UpdateScript:
     """Represents an update script."""
diff --git a/fietsboek/updater/cli.py b/fietsboek/updater/cli.py
index 45655d4..c71ec17 100644
--- a/fietsboek/updater/cli.py
+++ b/fietsboek/updater/cli.py
@@ -27,10 +27,17 @@ config_option = click.option(
 )
 
 
-def user_confirm():
+def user_confirm(verb):
+    """Ask the user for confirmation before proceeding.
+
+    Aborts the program if no confirmation is given.
+
+    :param verb: The verb to use in the text.
+    :type verb: str
+    """
     click.secho("Warning:", fg="yellow")
     click.echo(
-        "Updating *may* cause data loss. Make sure to have a backup of the "
+        f"{verb} *may* cause data loss. Make sure to have a backup of the "
         "database and the data directory!"
     )
     click.echo("For more information, please consult the documentation.")
@@ -79,8 +86,12 @@ def update(ctx, config, version, force):
         version = heads[0]
 
     click.echo(f"Selected version: {version}")
+    if updater.has_applied(version):
+        click.secho("Nothing to do", fg="green")
+        ctx.exit()
+
     if not force:
-        user_confirm()
+        user_confirm("Updating")
     updater.upgrade(version)
     version_str = ", ".join(updater.current_versions())
     click.secho(f"Update succeeded, version: {version_str}", fg="green")
@@ -111,8 +122,11 @@ def downgrade(ctx, config, version, force):
     version_str = ", ".join(updater.current_versions())
     click.echo(f"Current version: {version_str}")
     click.echo(f"Downgrade to version {version}")
+    if updater.has_applied(version, backward=True):
+        click.secho("Nothing to do", fg="green")
+        ctx.exit()
     if not force:
-        user_confirm()
+        user_confirm("Downgrading")
     updater.downgrade(version)
     version_str = ", ".join(updater.current_versions())
     click.secho(f"Downgrade succeeded, version: {version_str}", fg="green")
-- 
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