clarify documentation on the A status oddity

docs/faq.rst

@@ -168,9 +168,9 @@ repo. It will then be able to check using CRCs and HMACs.
 I am seeing 'A' (added) status for a unchanged file!?
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-The files cache (which is used to determine whether |project_name| already
-"knows" / has backed up a file and if so, to skip the file from chunking)
-does intentionally *not* contain files that:
+The files cache is used to determine whether |project_name| already
+"knows" / has backed up a file and if so, to skip the file from
+chunking. It does intentionally *not* contain files that:
 
 - have >= 10 as "entry age" (|project_name| has not seen this file for a while)
 - have a modification time (mtime) same as the newest mtime in the created
@@ -191,6 +191,10 @@ will often be the same and already stored in the repo (except in the above
 mentioned rare condition), it will just re-use them as usual and not store new
 data chunks.
 
+Since only the files cache is used in the display of files status,
+those files are reported as being added when, really, chunks are
+already used.
+
 Why was Borg forked from Attic?
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