Allow flymake diagnostic types to have shorter names

Eglot, a third-party package which uses Flymake, has its own
diagnostic types such as 'eglot-error', 'eglot-warning', etc...  While
not being too long, they will not fit in the type column of the "list
all diagnostics" buffer.  This commit allows diagnostic types to have
user-defined names and also assigns names to the default categories.

* doc/misc/flymake.texi (Flymake error types): Describe
flymake-type-name prop.

* lisp/progmodes/flymake.el (flymake--diagnostics-buffer-entries):
Use type names.
(flymake-error, flymake-warning, flymake-note): Give these
diagnostic categories default type names.

1 files changed, 5 insertions, 0 deletions

diff --git a/doc/misc/flymake.texi b/doc/misc/flymake.texi
index cedf1d84f90..21653b4a6d0 100644
--- a/doc/misc/flymake.texi
+++ b/doc/misc/flymake.texi
@@ -337,6 +337,11 @@ error.  If the overlay property @code{priority} is not specified in
 it and help sort overlapping overlays.
 
 @item
+@vindex flymake-type-name
+@code{flymake-type-name} is a string used to succinctly name the error
+type, in case the name of the symbol associated with it is very long.
+
+@item
 @vindex flymake-category
 @code{flymake-category} is a symbol whose property list is considered
 the default for missing values of any other properties.