[PATCH] Document colonless numeric history expansion word designators

[Éric NICOLAS <ccjmne@xxxxxxxxx>]

Using history expansion, the implementation of Zsh allows the omission
of the colon before some numeric word designators, following:

    !!, !#, and !?str?, for example !!2, !#1, and !?test?4:t.

The implementation has been exhibiting that behaviour since the earliest
revision in this Git repository, with e74702b46 (Initial revision,
1999-04-15), but the manual currently says that the colon may only be
omitted before:

    ^, $, *, -, or %.

For example, you may very well do:

    mkdir /tmp/asdf && cd !#1

Document the long-standing behaviour and introduce test coverage.

---
I wrote to the zsh-users mailing list in April this year, asking for
confirmation this behaviour is intended and here to stay.

This patch proposes to document that behaviour, which has been in place
throughout the entire recorded history of Zsh's source.

For reference, here's my thread: https://www.zsh.org/mla/users/2026/msg00148.html
---
 Doc/Zsh/expn.yo      |  7 +++++--
 Test/W01history.ztst | 14 ++++++++++++++
 2 files changed, 19 insertions(+), 2 deletions(-)

diff --git a/Doc/Zsh/expn.yo b/Doc/Zsh/expn.yo
index c5995f4e4..86edcddd0 100644
--- a/Doc/Zsh/expn.yo
+++ b/Doc/Zsh/expn.yo
@@ -184,8 +184,11 @@ cindex(word designators, history)
 A word designator indicates which word or words of a given command line are
 to be included in a history reference.  A `tt(:)' usually
 separates the event specification from the word designator.
-It may be omitted only if the word designator begins with a
-`tt(^)', `tt($)', `tt(*)', `tt(-)' or `tt(%)'.
+It may be omitted if the word designator begins with a `tt(^)', `tt($)',
+`tt(*)', `tt(-)' or `tt(%)'.  A numeric word designator may also omit the colon
+after `tt(!!)', `tt(!#)', or a `tt(!?)var(str)tt(?)' event designator, for
+example `tt(!!3)', `tt(!#3)' or `tt(!?)var(str)tt(?3)'.  Note that `tt(!3)'
+refers to event 3 rather than word 3 of the previous event.
 Word designators include:
 
 startsitem()
diff --git a/Test/W01history.ztst b/Test/W01history.ztst
index 665a37f2c..272b5a435 100644
--- a/Test/W01history.ztst
+++ b/Test/W01history.ztst
@@ -18,6 +18,20 @@
 >one two three four five six seven eight nine ten
 >print one two three four five six seven eight nine ten one two
 
+  PS1= $ZTST_testdir/../Src/zsh -fis <<<'
+    print huey dewey louie
+    print !!2
+    print /tmp/asdf !#1
+    print test a/one b/two c/three
+    print !?test?4:t
+  '
+0:Numeric word references without a colon
+>huey dewey louie
+>dewey
+>/tmp/asdf /tmp/asdf
+>test a/one b/two c/three
+>three
+
   PS1= $ZTST_testdir/../Src/zsh -fis <<<'
     print line one of an arbitrary series
     print issue two for some mystery sequence
-- 
2.55.0