manifestcache: test that adding the same entry twice do not duplicates it

Simple sanity check.

tests/test-manifest.t

@@ -1,118 +1,126 b''
 Source bundle was generated with the following script:
 
 # hg init
 # echo a > a
 # ln -s a l
 # hg ci -Ama -d'0 0'
 # mkdir b
 # echo a > b/a
 # chmod +x b/a
 # hg ci -Amb -d'1 0'
 
   $ hg init
   $ hg unbundle "$TESTDIR/bundles/test-manifest.hg"
   adding changesets
   adding manifests
   adding file changes
   added 2 changesets with 3 changes to 3 files
   new changesets b73562a03cfe:5bdc995175ba (2 drafts)
   (run 'hg update' to get a working copy)
 
 The next call is expected to return nothing:
 
   $ hg manifest
 
   $ hg co
   3 files updated, 0 files merged, 0 files removed, 0 files unresolved
 
   $ hg manifest
   a
   b/a
   l
 
   $ hg files -vr .
            2   a
            2 x b/a
            1 l l
   $ hg files -r . -X b
   a
   l
   $ hg files -T '{path} {size} {flags}\n'
   a 2 
   b/a 2 x
   l 1 l
   $ hg files -T '{path} {node|shortest}\n' -r.
   a 5bdc
   b/a 5bdc
   l 5bdc
 
   $ hg manifest -v
   644   a
   755 * b/a
   644 @ l
   $ hg manifest -T '{path} {rev}\n'
   a 1
   b/a 1
   l 1
 
   $ hg manifest --debug
   b789fdd96dc2f3bd229c1dd8eedf0fc60e2b68e3 644   a
   b789fdd96dc2f3bd229c1dd8eedf0fc60e2b68e3 755 * b/a
   047b75c6d7a3ef6a2243bd0e99f94f6ea6683597 644 @ l
 
   $ hg manifest -r 0
   a
   l
 
   $ hg manifest -r 1
   a
   b/a
   l
 
   $ hg manifest -r tip
   a
   b/a
   l
 
   $ hg manifest tip
   a
   b/a
   l
 
   $ hg manifest --all
   a
   b/a
   l
 
 The next two calls are expected to abort:
 
   $ hg manifest -r 2
   abort: unknown revision '2'!
   [255]
 
   $ hg manifest -r tip tip
   abort: please specify just one revision
   [255]
 
 Testing the manifest full text cache utility
 --------------------------------------------
 
 Reminder of the manifest log content
 
   $ hg log --debug | grep 'manifest:'
   manifest:    1:1e01206b1d2f72bd55f2a33fa8ccad74144825b7
   manifest:    0:fce2a30dedad1eef4da95ca1dc0004157aa527cf
 
 Showing the content of the caches after the above operations
 
   $ hg debugmanifestfulltextcache
   cache empty
 
 Adding a new persistent entry in the cache
 
   $ hg debugmanifestfulltextcache --add 1e01206b1d2f72bd55f2a33fa8ccad74144825b7
 
   $ hg debugmanifestfulltextcache
   cache contains 1 manifest entries, in order of most to least recent:
   id: 1e01206b1d2f72bd55f2a33fa8ccad74144825b7, size 133 bytes
   total cache data size 157 bytes, on-disk 157 bytes
+
+Check we don't duplicated entry (added from the debug command)
+
+  $ hg debugmanifestfulltextcache --add 1e01206b1d2f72bd55f2a33fa8ccad74144825b7
+  $ hg debugmanifestfulltextcache
+  cache contains 1 manifest entries, in order of most to least recent:
+  id: 1e01206b1d2f72bd55f2a33fa8ccad74144825b7, size 133 bytes
+  total cache data size 157 bytes, on-disk 157 bytes