docs: add a note of why CACHEDIR.TAG itself gets backed up

Sponsored-by: author

1 files changed, 3 insertions, 1 deletions

diff --git a/obnam.md b/obnam.md
index a6f9b4c..396bc44 100644
--- a/obnam.md
+++ b/obnam.md
@@ -1793,7 +1793,9 @@ roots:
 ### By default, skip directories containing CACHEDIR.TAG
 
 This scenario verifies that Obnam client skips the contents of directories that
-contain [CACHEDIR.TAG][], but backs up the tag itself.
+contain [CACHEDIR.TAG][], but backs up the tag itself. We back up the
+tag so that after a restore, the directory continues to be tagged as a
+cache directory.
 
 [CACHEDIR.TAG]: https://bford.info/cachedir/