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+#	@(#)context	8.5 (Berkeley) 7/23/94
+
+In historic vi, the previous context mark was always set:
+
+ex address:
+    any number, <question-mark>, <slash>, <dollar-sign>,
+    <single-quote>, <backslash>
+
+ex commands: undo, "z.", global, vglobal
+
+vi commands: (, ), {, }, %, [[, ]], ^]
+
+nvi adds the vi command ^T to this list.
+
+=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
+In historic vi, the previous context mark was set if the
+line changed:
+
+vi commands: '<mark>, G, H, L, M, z
+
+=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
+In historic vi, the previous context mark was set if the
+line or column changed:
+
+vi commands: `<mark>, /, ?, N, n
+
+nvi adds the vi command ^A to this list.
+
+=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
+In historic vi, the previous context mark was set in non-visual
+mode for ^R and ^L if the line changed, but I have yet to figure
+out how the line could change.