Strip "./" prefix from fd output in projectile-files-via-ext-command

Newer fd versions (8.3.0+) prepend "./" to output.  The --strip-cwd-prefix
flag was already added to projectile-generic-command and projectile-git-fd-args,
but this flag doesn't exist in older fd versions, causing errors.

Add post-processing in projectile-files-via-ext-command to strip the "./"
prefix from results as a defensive fallback, matching the existing pattern
in projectile-files-from-cmd.

Fixes #1749

Author: bbatsov

CHANGELOG.md

@@ -9,6 +9,7 @@
 ### Bugs fixed
 
 * [#1961](https://github.com/bbatsov/projectile/issues/1961): Prevent directories from matching file-type project root markers (e.g., a `workspace` directory no longer matches the `WORKSPACE` Bazel marker on case-insensitive filesystems).
+* [#1749](https://github.com/bbatsov/projectile/issues/1749): Strip `./` prefix from `fd` output in `projectile-files-via-ext-command`, fixing compatibility with older `fd` versions that don't support `--strip-cwd-prefix`.
 
 ### Changes
 

projectile.el

@@ -1661,7 +1661,11 @@ Only text sent to standard output is taken into account."
       (with-temp-buffer
         (shell-command command t "*projectile-files-errors*")
         (let ((shell-output (buffer-substring (point-min) (point-max))))
-          (split-string (string-trim shell-output) "\0" t))))))
+          (mapcar (lambda (f)
+                    (if (string-prefix-p "./" f)
+                        (substring f 2)
+                      f))
+                  (split-string (string-trim shell-output) "\0" t)))))))
 
 (defun projectile-adjust-files (project vcs files)
   "First remove ignored files from FILES, then add back unignored files."

test/projectile-test.el

@@ -546,7 +546,11 @@ Just delegates OPERATION and ARGS for all operations except for`shell-command`'.
               (expect (projectile-files-via-ext-command "" "echo filename") :to-equal '("filename")))
 
           (it "supports magic file handlers"
-              (expect (projectile-files-via-ext-command "#magic#" "echo filename") :to-equal '("magic"))))
+              (expect (projectile-files-via-ext-command "#magic#" "echo filename") :to-equal '("magic")))
+
+          (it "strips ./ prefix from results"
+              (expect (projectile-files-via-ext-command "" "printf './foo\\0./bar/baz\\0quux'")
+                      :to-equal '("foo" "bar/baz" "quux"))))
 
 (describe "projectile-mode"
   (before-each