Honor tags-case-fold-search during xref identifer completion

* etc/NEWS: New entry.

* lisp/progmodes/etags.el (tags-case-fold-search):
Mark as safe-local.
(find-tag--completion-ignore-case):
Extract from tags-completion-at-point-function, find-tag-tag and
etags--xref-find-definitions.
(xref-backend-identifier-completion-ignore-case):
New method. Use it here as well.

* lisp/progmodes/xref.el
(xref-backend-identifier-completion-ignore-case): New generic.
(xref--read-identifier): Use it here.

1 files changed, 4 insertions, 0 deletions

diff --git a/etc/NEWS b/etc/NEWS
index 69ffcdb66e5..1494fab47a8 100644
--- a/etc/NEWS
+++ b/etc/NEWS
@@ -1458,6 +1458,10 @@ A new command 'xref-revert-buffer' is bound to 'g'.
 ---
 *** Imenu support has been added to 'xref--xref-buffer-mode'.
 
+*** New generic method 'xref-backend-identifier-completion-ignore-case'.
+Using it, the etags backend now honors 'tags-case-fold-search' during
+identifier completion.
+
 ** Checkdoc
 
 ---