; Fix failing diff-mode tests

* test/lisp/vc/diff-mode-resources/git.patch: Delete file, moving
its contents to...
* test/lisp/vc/diff-mode-tests.el (diff-mode-tests--git-patch):
...this new variable.  Git merges kept deleting a trailing
whitespace in the patch signature, so let's do this instead.
(diff-mode-test-git-patch)
(diff-mode-test-git-patch/before-first-hunk)
(diff-mode-test-git-patch/signature): Use above new variable.

test/lisp/vc/diff-mode-resources/git.patch

@@ -1,51 +0,0 @@
-From 1234567890abcdef1234567890abcdef12345678 Mon Sep 17 00:00:00 2001
-From: Alyssa P. Hacker <alyssa.p.hacker@example.com>
-Date: Sun, 3 Mar 2025 10:30:00 -0400
-Subject: [PATCH] Subtle bug fixes and slight improvements
-
-- This is not a removed line
-+ This is not an added line
-
----
- src/main.py | 10 +++++-----
- 1 file changed, 5 insertions(+), 5 deletions(-)
-
-diff --git a/src/main.py b/src/main.py
-index 9f6c5fe43e47eab441232e54456c5c2b06297b65..7b3f91a8b4ed923c8f43183276e3ab36fe04f6c9 100644
---- a/src/main.py
-+++ b/src/main.py
-@@ -2,25 +2,24 @@
-
- def main():
-     # Initialize the magic number generator
--    magic_number = 42
--    print("Magic number: ", magic_number)
-
--    # TODO: Fix the infinite loop
--    while True:
--        print("This loop will never end")
-+    magic_number = 73  # After reconsidering, 73 seems more appropriate
-+    print("Updated magic number: ", magic_number)
-
-+    # The infinite loop was probably not the best approach
-+    # while True:
-+    #     print("This loop will never end.")
-
-     # This part of the code handles other important tasks
-     print("Processing other tasks...")
-
-     # Error handling has been updated for clarity
--    if not fixed_it_yet:
--        print("ERROR: Still broken!")
-+    if not fixed_it_yet:  # This should be fine now
-+        print("ERROR: No longer an issue.")
-
-     # Exiting the function on a positive note
--    print("Goodbye, cruel world!")
-+    print("Goodbye, world!")
-
- if __name__ == "__main__":
-     main()
-
---
-2.40.0

test/lisp/vc/diff-mode-tests.el

@@ -557,10 +557,63 @@ baz"))))
 +1
 ")))))
 
+(defvar diff-mode-tests--git-patch
+  "From 1234567890abcdef1234567890abcdef12345678 Mon Sep 17 00:00:00 2001
+From: Alyssa P. Hacker <alyssa.p.hacker@example.com>
+Date: Sun, 3 Mar 2025 10:30:00 -0400
+Subject: [PATCH] Subtle bug fixes and slight improvements
+
+- This is not a removed line
++ This is not an added line
+
+---
+ src/main.py | 10 +++++-----
+ 1 file changed, 5 insertions(+), 5 deletions(-)
+
+diff --git a/src/main.py b/src/main.py
+index 9f6c5fe43e47eab441232e54456c5c2b06297b65..7b3f91a8b4ed923c8f43183276e3ab36fe04f6c9 100644
+--- a/src/main.py
++++ b/src/main.py
+@@ -2,25 +2,24 @@
+
+ def main():
+     # Initialize the magic number generator
+-    magic_number = 42
+-    print(\"Magic number: \", magic_number)
+
+-    # TODO: Fix the infinite loop
+-    while True:
+-        print(\"This loop will never end\")
++    magic_number = 73  # After reconsidering, 73 seems more appropriate
++    print(\"Updated magic number: \", magic_number)
+
++    # The infinite loop was probably not the best approach
++    # while True:
++    #     print(\"This loop will never end.\")
+
+     # This part of the code handles other important tasks
+     print(\"Processing other tasks...\")
+
+     # Error handling has been updated for clarity
+-    if not fixed_it_yet:
+-        print(\"ERROR: Still broken!\")
++    if not fixed_it_yet:  # This should be fine now
++        print(\"ERROR: No longer an issue.\")
+
+     # Exiting the function on a positive note
+-    print(\"Goodbye, cruel world!\")
++    print(\"Goodbye, world!\")
+
+ if __name__ == \"__main__\":
+     main()
+
+--\s
+2.40.0
+")
+
 (ert-deftest diff-mode-test-git-patch ()
-  (let ((file (ert-resource-file "git.patch")))
   (with-temp-buffer
-     (insert-file-contents file)
+    (insert diff-mode-tests--git-patch)
     (diff-mode)
     (font-lock-ensure)
     (goto-char (point-min))
@@ -569,12 +622,11 @@ baz"))))
                 'diff-removed))
     (re-search-forward "magic_number = 73")
     (should (eq (get-text-property (match-beginning 0) 'face)
-                 'diff-added)))))
+                'diff-added))))
 
 (ert-deftest diff-mode-test-git-patch/before-first-hunk ()
-  (let ((file (ert-resource-file "git.patch")))
   (with-temp-buffer
-     (insert-file-contents file)
+    (insert diff-mode-tests--git-patch)
     (diff-mode)
     (font-lock-ensure)
     (goto-char (point-min))
@@ -584,18 +636,17 @@ baz"))))
     (re-search-forward "This is not an added line")
     (font-lock-ensure)
     (should (eq (get-text-property (match-beginning 0) 'face)
-                 'diff-context)))))
+                'diff-context))))
 
 (ert-deftest diff-mode-test-git-patch/signature ()
-  (let ((file (ert-resource-file "git.patch")))
   (with-temp-buffer
-     (insert-file-contents file)
+    (insert diff-mode-tests--git-patch)
     (diff-mode)
     (font-lock-ensure)
     (goto-char (point-max))
     (re-search-backward "^-- $")
     (should (eq (get-text-property (match-beginning 0) 'face)
-                  'diff-context)))))
+                'diff-context))))
 
 (ert-deftest diff-mode-test-topmost-addition-undo ()
   (let ((patch "diff --git a/fruits b/fruits