+
−  $ hg init
+
−
+
−  $ cat > .hg/hgrc <<EOF
+
−  > [extensions]
+
−  > prefixfilter = prefix.py
+
−  > [encode]
+
−  > *.txt = stripprefix: Copyright 2046, The Masters
+
−  > [decode]
+
−  > *.txt = insertprefix: Copyright 2046, The Masters
+
−  > EOF
+
−
+
−  $ cat > prefix.py <<EOF
+
−  > from mercurial import error
+
−  > def stripprefix(s, cmd, filename, **kwargs):
+
−  >     header = b'%s\n' % cmd
+
−  >     if s[:len(header)] != header:
+
−  >         raise error.Abort(b'missing header "%s" in %s' % (cmd, filename))
+
−  >     return s[len(header):]
+
−  > def insertprefix(s, cmd):
+
−  >     return b'%s\n%s' % (cmd, s)
+
−  > def reposetup(ui, repo):
+
−  >     repo.adddatafilter(b'stripprefix:', stripprefix)
+
−  >     repo.adddatafilter(b'insertprefix:', insertprefix)
+
−  > EOF
+
−
+
−  $ cat > .hgignore <<EOF
+
−  > .hgignore
+
−  > prefix.py
+
−  > prefix.pyc
+
−  > __pycache__/
+
−  > EOF
+
−
+
−  $ cat > stuff.txt <<EOF
+
−  > Copyright 2046, The Masters
+
−  > Some stuff to ponder very carefully.
+
−  > EOF
+
−  $ hg add stuff.txt
+
−  $ hg ci -m stuff
+
−
+
−Repository data:
+
−
+
−  $ hg cat stuff.txt
+
−  Some stuff to ponder very carefully.
+
−
+
−Fresh checkout:
+
−
+
−  $ rm stuff.txt
+
−  $ hg up -C
+
−  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
+
−  $ cat stuff.txt
+
−  Copyright 2046, The Masters
+
−  Some stuff to ponder very carefully.
+
−  $ echo "Very very carefully." >> stuff.txt
+
−  $ hg stat
+
−  M stuff.txt
+
−
+
−  $ echo "Unauthorized material subject to destruction." > morestuff.txt
+
−
+
−Problem encoding:
+
−
+
−  $ hg add morestuff.txt
+
−  $ hg ci -m morestuff
+
−  abort: missing header "Copyright 2046, The Masters" in morestuff.txt
+
−  [255]
+
−  $ hg stat
+
−  M stuff.txt
+
−  A morestuff.txt