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+<a id="dir-spec.txt-E"></a>
+
+# Limited ed diff format
+
+We support the following format for consensus diffs.  It's a
+subset of the ed diff format, but clients MUST NOT accept other
+ed commands.
+
+We support the following ed commands, each on a line by itself:
+
+```text
+    - "<n1>d"          Delete line n1
+    - "<n1>,<n2>d"     Delete lines n1 through n2, inclusive
+    - "<n1>,$d"        Delete line n1 through the end of the file, inclusive.
+    - "<n1>c"          Replace line n1 with the following block
+    - "<n1>,<n2>c"     Replace lines n1 through n2, inclusive, with the
+                       following block.
+    - "<n1>a"          Append the following block after line n1.
+```
+
+Note that line numbers always apply to the file after all previous
+commands have already been applied.  Note also that line numbers
+are 1-indexed.
+
+The commands MUST apply to the file from back to front, such that
+lines are only ever referred to by their position in the original
+file.
+
+If there are any directory signatures on the original document, the
+first command MUST be a "`<n1>,$d`" form to remove all of the directory
+signatures.  Using this format ensures that the client will
+successfully apply the diff even if they have an unusual encoding for
+the signatures.
+
+The replace and append command take blocks.  These blocks are simply
+appended to the diff after the line with the command.  A line with
+just a period (".") ends the block (and is not part of the lines
+to add).  Note that it is impossible to insert a line with just
+a single dot.