[clangd] FuzzyMatch: forbid tail-tail matches after a miss: [pat] !~ "panther"

Summary:
This is a small code change but vastly reduces noise in code completion results.
The intent of allowing this was to let [sc] ~ "strncpy" and [strcpy] ~ "strncpy"
however the benefits for unsegmented names aren't IMO worth the costs.

Test cases should be representative of the changes here.

Reviewers: ilya-biryukov

Subscribers: ioeric, MaskRay, jkorous, cfe-commits

Differential Revision: https://reviews.llvm.org/D47950

git-svn-id: https://llvm.org/svn/llvm-project/clang-tools-extra/trunk@334712 91177308-0d34-0410-b5e6-96231b3b80d8
4 files changed