bug#65137: 29.1; completion-substring-try-completion doesn't return the longest common substring

[Dmitry Gutov <dmitry@gutov.dev>]

Hi Spencer!

On 08/08/2023 02:24, Spencer Baugh wrote:
> However, even this does not work in the project-file and xref-location
> completion categories, for which the "basic" style is not included in
> completion-category-defaults.  For such completion categories, there's
> simply no way to use completion to insert a common prefix.  This is bad,
> because a filename or identifier might easily be a prefix of another
> filename or identifier.

Could you describe the usage scenario a little more?

 From my brief testing, the current behavior seems okay most of the 
time: you still get the short input which matches a bunch of strings 
(e.g. filenames), you can type a little more chars and narrow down.

With your change, TAB will insert the most common prefix for all those 
completions, which in case of project-file can be a pretty long string. 
Not a huge problem, but on the face of it that doesn't seem like an 
improvement. So which scenario would that make better?