#	@(#)context	8.6 (Berkeley) 10/14/94

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, v

vi commands: (, ), {, }, %, [[, ]], ^]

nvi adds the vi command ^T to this list.

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In historic vi, the previous context mark was set if the
line changed:

vi commands: '<mark>, G, H, L, M, z

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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.

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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.