bug#1512: 23.0.60; SPC, TAB during completion do not do word completion, prefix completion

[Drew Adams]

emacs -Q
 
1. Suppose that you have a command `g-spot-marks-the-spot', and you
do this, mistakenly typing `c' instead of `s': `M-x g-c SPC'

There are no word completions for `g-c'. However, instead of Emacs
saying "[No match]", many possible partial-completion matches are
shown. SPC no longer provides word completion by default. You no
longer get useful feedback letting you know that you typed the
wrong character.
 
Prior to Emacs 23, both regular prefix completion and word completion
were available by default: TAB for the former, SPC for the latter.
Partial-completion mode was optional.
 
This traditional behavior (since the beginning of Emacs) should
remain the default behavior. Users should not have to customize
`completion-styles' just to restore the standard completion.

Those who prefer that SPC perform partial completion should opt in
for it, as before. Now they would also have the choice of customizing
`completion-styles' to include `partial-completion', in addition to
the choice of turning on `partial-completion-mode'.


2. A similar problem arises for prefix (i.e. TAB) completion. If you
have a command named `in-the-final-act' and you type `g' by mistake
instead of `t': `M-x in-g TAB', then instead of Emacs letting you
know that there is no match, so you can delete the `g' and type a
`t', Emacs completes your input to `inverse-add-global-abbrev',
which is confusing and, once you figure things out, requires much
more editing to get you back on track. With multiple partial
completion matches, the problem is compounded.


Please restore the traditional Emacs completion behavior by default.
It provides helpful feedback that lets you quickly correct typos on
the fly. And it is what Emacs users are used to. Users who want
partial completion turned on can customize Emacs to get that.

 
In GNU Emacs 23.0.60.1 (i386-mingw-nt5.1.2600)
 of 2008-11-24 on LENNART-69DE564
Windowing system distributor `Microsoft Corp.', version 5.1.2600
configured using `configure --with-gcc (3.4) --no-opt --cflags -Ic:/g/include
-fno-crossjumping'