Allow multiple root-dirs to be search by projectile-grep

When a project is configured via `.projectile` to include multiple directories
explicitly this results in `projectile-grep` to run over multiple roots.

```
+/foo/bar
+/baz/
```

With a single global *grep* buffer this results in either

a) losing all but the search result of the last root
b) Stalling as the user is asked per root to kill the grep buffer

To avoid this the name of the `*grep*` buffer should to include the current
`root` being search associated with the buffer like `*grep <~/source/foo/bar>*`.

3 files changed, 35 insertions, 1 deletions

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 9aec45a..5b00d2d 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -21,6 +21,7 @@
 * [#1385](https://github.com/bbatsov/projectile/issues/1385): Update `projectile-replace` for Emacs 27.
 * [#1432](https://github.com/bbatsov/projectile/issues/1432): Support .NET project.
 * [#1270](https://github.com/bbatsov/projectile/issues/1270): Fix running commands that don't have a default value.
+* [#1482](https://github.com/bbatsov/projectile/issues/1482): Run a seperate grep buffer per project root
 
 ## 2.0.0 (2019-01-01)
 
diff --git a/projectile.el b/projectile.el
index 368f2e4..0ee15b1 100644
--- a/projectile.el
+++ b/projectile.el
@@ -3206,7 +3206,13 @@ With REGEXP given, don't query the user for a regexp."
               (projectile-grep-find-unignored-patterns (projectile-patterns-to-ensure)))
           (grep-compute-defaults)
           (cl-letf (((symbol-function 'rgrep-default-command) #'projectile-rgrep-default-command))
-            (rgrep search-regexp (or files "* .*") root-dir)))))
+            (rgrep search-regexp (or files "* .*") root-dir)
+            (when (get-buffer "*grep*")
+              ;; When grep is using a global *grep* buffer rename it to be
+              ;; scoped to the current root to allow multiple concurrent grep
+              ;; operations, one per root
+              (with-current-buffer "*grep*"
+                (rename-buffer (concat "*grep <" root-dir ">*"))))))))
     (run-hooks 'projectile-grep-finished-hook)))
 
 ;;;###autoload
diff --git a/test/projectile-test.el b/test/projectile-test.el
index 0d56c57..32b915d 100644
--- a/test/projectile-test.el
+++ b/test/projectile-test.el
@@ -28,6 +28,7 @@
 (require 'projectile)
 (require 'buttercup)
 
+
 (message "Running tests on Emacs %s" emacs-version)
 
 ;; TODO: Revise this init logic
@@ -643,6 +644,32 @@ You'd normally combine this with `projectile-test-with-sandbox'."
         (expect (projectile-project-root) :to-equal correct-project-root))))))
 
 (describe "projectile-grep"
+  (describe "multi-root grep"
+    (after-each
+      (cl-flet ((grep-buffer-p (b) (string-prefix-p "*grep" (buffer-name b))))
+        (let ((grep-buffers (cl-remove-if-not #'grep-buffer-p (buffer-list))))
+          (dolist (grep-buffer grep-buffers)
+            (let ((kill-buffer-query-functions nil))
+              (kill-buffer grep-buffer))))))
+    (it "grep multi-root projects"
+      (projectile-test-with-sandbox
+        (projectile-test-with-files
+            ("project/bar/"
+             "project/baz/")
+          (cd "project")
+          (with-temp-file ".projectile" (insert (concat "+/baz\n"
+                                                        "+/bar\n")))
+          (with-temp-file "foo.txt" (insert "hi"))
+          (with-temp-file "bar/bar.txt" (insert "hi"))
+          (with-temp-file "baz/baz.txt" (insert "hi"))
+          (with-current-buffer (find-file-noselect ".projectile" t)
+            (let ((grep-find-template "<X>")
+                  grep-find-ignored-directories grep-find-ignored-files
+                  projectile-globally-ignored-files
+                  projectile-globally-ignored-file-suffixes
+                  projectile-globally-ignored-directories)
+              (projectile-grep "hi")))))))
+
   (describe "rgrep"
     (before-each
       (spy-on 'compilation-start))