Add `--prune` switch to `forget`

doc/Manual.md

@@ -545,7 +545,8 @@ be done either manually (by specifying a snapshot ID to remove) or by using a
 policy that describes which snapshots to forget. For all remove operations, two
 commands need to be called in sequence: `forget` to remove a snapshot and
 `prune` to actually remove the data that was referenced by the snapshot from
-the repository.
+the repository. This can be automated with the `--prune` option of the `forget`
+command, which runs `prune` automatically if snapshots have been removed.
 
 ## Remove a single snapshot
 
@@ -610,6 +611,41 @@ done
 
 Afterwards the repository is smaller.
 
+You can automate this two-step process by using the `--prune` switch to
+`forget`:
+
+```console
+$ restic forget --keep-last 1 --prune
+snapshots for host mopped, directories /home/user/work:
+
+keep 1 snapshots:
+ID        Date                 Host        Tags        Directory
+----------------------------------------------------------------------
+4bba301e  2017-02-21 10:49:18  mopped                  /home/user/work
+
+remove 1 snapshots:
+ID        Date                 Host        Tags        Directory
+----------------------------------------------------------------------
+8c02b94b  2017-02-21 10:48:33  mopped                  /home/user/work
+
+1 snapshots have been removed, running prune
+counting files in repo
+building new index for repo
+[0:00] 100.00%  37 / 37 packs
+repository contains 37 packs (5521 blobs) with 151.012 MiB bytes
+processed 5521 blobs: 0 duplicate blobs, 0B duplicate
+load all snapshots
+find data that is still in use for 1 snapshots
+[0:00] 100.00%  1 / 1 snapshots
+found 5323 of 5521 data blobs still in use, removing 198 blobs
+will delete 0 packs and rewrite 27 packs, this frees 22.106 MiB
+creating new index
+[0:00] 100.00%  30 / 30 packs
+saved new index as b49f3e68
+done
+```
+
+
 ## Removing snapshots according to a policy
 
 Removing snapshots manually is tedious and error-prone, therefore restic allows
@@ -747,4 +783,4 @@ enter password for repository:
 Restic supports the output of some commands in JSON format. The JSON flag ```--json``` is currently supported only by ```restic snapshots```.
 
 ```console
-$ restic -r /tmp/backup snapshots --json```
+$ restic -r /tmp/backup snapshots --json```

src/cmds/restic/cmd_forget.go

@@ -38,6 +38,7 @@ type ForgetOptions struct {
 	Tags     []string
 
 	DryRun bool
+	Prune  bool
 }
 
 var forgetOptions ForgetOptions
@@ -58,6 +59,7 @@ func init() {
 	f.StringSliceVar(&forgetOptions.Tags, "tag", []string{}, "only forget snapshots with the `tag` (can be specified multiple times)")
 
 	f.BoolVarP(&forgetOptions.DryRun, "dry-run", "n", false, "do not delete anything, just print what would be done")
+	f.BoolVar(&forgetOptions.Prune, "prune", false, "automatically run the 'prune' command if snapshots have been removed")
 }
 
 func printSnapshots(w io.Writer, snapshots restic.Snapshots) {
@@ -188,6 +190,7 @@ func runForget(opts ForgetOptions, gopts GlobalOptions, args []string) error {
 		snapshotGroups[k] = list
 	}
 
+	removeSnapshots := 0
 	for key, snapshotGroup := range snapshotGroups {
 		Printf("snapshots for host %v, directories %v:\n\n", key.Hostname, key.Dirs)
 		keep, remove := restic.ApplyPolicy(snapshotGroup, policy)
@@ -200,6 +203,8 @@ func runForget(opts ForgetOptions, gopts GlobalOptions, args []string) error {
 		printSnapshots(globalOptions.stdout, remove)
 		Printf("\n")
 
+		removeSnapshots += len(remove)
+
 		if !opts.DryRun {
 			for _, sn := range remove {
 				h := restic.Handle{Type: restic.SnapshotFile, Name: sn.ID().String()}
@@ -211,5 +216,12 @@ func runForget(opts ForgetOptions, gopts GlobalOptions, args []string) error {
 		}
 	}
 
+	if removeSnapshots > 0 && opts.Prune {
+		Printf("%d snapshots have been removed, running prune\n", removeSnapshots)
+		if !opts.DryRun {
+			return pruneRepository(gopts, repo)
+		}
+	}
+
 	return nil
 }

src/cmds/restic/cmd_prune.go

@@ -75,7 +75,11 @@ func runPrune(gopts GlobalOptions) error {
 		return err
 	}
 
-	err = repo.LoadIndex()
+	return pruneRepository(gopts, repo)
+}
+
+func pruneRepository(gopts GlobalOptions, repo restic.Repository) error {
+	err := repo.LoadIndex()
 	if err != nil {
 		return err
 	}