Fix #2: support pruning and forget via snapshot policies

README.md

@@ -10,6 +10,7 @@ Autorestic is a wrapper around the amazing [restic](https://restic.net/). While
 - Config files, no CLI
 - Predictable
 - Backup locations to multiple backends
+- Snapshot policies and pruning
 - Simple interface
 - Fully encrypted
 
@@ -32,7 +33,7 @@ locations:
   home:
     from: /home/me
     to: remote
-  
+
   important:
     from: /path/to/important/stuff
     to:
@@ -45,7 +46,7 @@ backends:
     path: 'myBucket:backup/home'
     B2_ACCOUNT_ID: account_id
     B2_ACCOUNT_KEY: account_key
-  
+
   hdd:
     type: local
     path: /mnt/my_external_storage
@@ -57,7 +58,7 @@ Then we check if everything is correct by running the `check` command. We will p
 autorestic check -a
 ```
 
-If we would check only one location we could run the following: `autorestic -l home check`. 
+If we would check only one location we could run the following: `autorestic -l home check`.
 
 ### Backup
 
@@ -108,7 +109,7 @@ For each backend you need to specify the right variables as shown in the example
 ##### `path`
 
 The path on the remote server.
-For object storages as 
+For object storages as
 
 ##### Example
 
@@ -121,9 +122,55 @@ backends:
     B2_ACCOUNT_KEY: backblaze_account_key
 ```
 
+## Pruning and snapshot policies
 
+Autorestic supports declaring snapshot policies for location to avoid keeping old snapshot around if you don't need them.
+
+This is based on [Restic's snapshots policies](https://restic.readthedocs.io/en/latest/060_forget.html#removing-snapshots-according-to-a-policy), and can be enabled for each location as shown below:
+
+```yaml
+locations:
+  etc:
+    from: /etc
+    to: local
+    keep:
+      # options matches the --keep-* options used in the restic forget CLI
+      # cf https://restic.readthedocs.io/en/latest/060_forget.html#removing-snapshots-according-to-a-policy
+      last: 5             # always keep at least 5 snapshots
+      hourly: 3           # keep 3 last hourly shapshots
+      daily: 4            # keep 4 last daily shapshots
+      weekly: 1           # keep 1 last weekly shapshots
+      monthly: 12         # keep 12 last monthly shapshots
+      yearly: 7           # keep 7 last yearly shapshots
+      within: "2w"        # keep snapshots from the last 2 weeks
+```
+
+Pruning can be triggered using `autorestic forget -a`, for all locations, or selectively with `autorestic forget -l <location>`. **please note that contrary to the restic CLI, `restic forget` will call `restic prune` internally.**
+
+
+
+Run with the `--dry-run` flag to only print information about the process without actually pruning the snapshots. This is especially useful for debugging or testing policies:
+
+```
+$ autorestic forget -a --dry-run --verbose
+
+Configuring Backends
+local : Done ✓
+
+Removing old shapshots according to policy
+etc ▶ local : Removing old spnapshots… ⏳
+etc ▶ local : Running in dry-run mode, not touching data
+etc ▶ local : Forgeting old snapshots… ⏳Applying Policy: all snapshots within 2d of the newest
+keep 3 snapshots:
+ID        Time                 Host        Tags        Reasons    Paths
+-----------------------------------------------------------------------------
+531b692a  2019-12-02 12:07:28  computer                within 2w  /etc
+51659674  2019-12-02 12:08:46  computer                within 2w  /etc
+f8f8f976  2019-12-02 12:11:08  computer                within 2w  /etc
+-----------------------------------------------------------------------------
+3 snapshots
+```
 
 ##### Note
 
 Note that the data is automatically encrypted on the server. The key will be generated and added to your config file. Every backend will have a separate key. You should keep a copy of the keys somewhere in case your server dies. Otherwise DATA IS LOST!
-