Provide tips about old-style flags for those on older versions.

docs/how-to/deal-with-very-large-backups.md

@@ -22,6 +22,9 @@ borgmatic create
 borgmatic check
 ```
 
+(No borgmatic `prune`, `create`, or `check` actions? Try the old-style
+`--prune`, `--create`, or `--check`. Or upgrade borgmatic!)
+
 You can run with only one of these flags provided, or you can mix and match
 any number of them in a single borgmatic run. This supports approaches like
 making backups with `create` on a frequent schedule, while only running

docs/how-to/inspect-your-backups.md

@@ -33,6 +33,9 @@ borgmatic list
 borgmatic info
 ```
 
+(No borgmatic `list` or `info` actions? Try the old-style `--list` or
+`--info`. Or upgrade borgmatic!)
+
 ## Logging
 
 By default, borgmatic logs to a local syslog-compatible daemon if one is

docs/how-to/restore-a-backup.md

@@ -11,6 +11,9 @@ to figure out which archive to restore. A good way to do that is to use the
 borgmatic list
 ```
 
+(No borgmatic `list` action? Try the old-style `--list`, or upgrade
+borgmatic!)
+
 That should yield output looking something like:
 
 ```text
@@ -25,6 +28,9 @@ and therefore the latest timestamp, run a command like:
 borgmatic extract --archive host-2019-01-02T04:06:07.080910
 ```
 
+(No borgmatic `extract` action? Try the old-style `--extract`, or upgrade
+borgmatic!)
+
 The `--archive` value is the name of the archive to restore. This extracts the
 entire contents of the archive to the current directory, so make sure you're
 in the right place before running the command.

docs/how-to/set-up-backups.md

@@ -124,6 +124,9 @@ a command like the following:
 borgmatic init --encryption repokey
 ```
 
+(No borgmatic `init` action? Try the old-style `--init` flag, or upgrade
+borgmatic!)
+
 This uses the borgmatic configuration file you created above to determine
 which local or remote repository to create, and encrypts it with the
 encryption passphrase specified there if one is provided. Read about [Borg