gnu: mtpaint: Fix version numbering.

* gnu/packages/image.scm (mtpaint): Remove let binding.
[version]: Don't use GIT-VERSION.
[source]: Specify the matching COMMIT directly.

gnu/packages/image.scm

@@ -2075,19 +2075,17 @@ AOM, including with alpha.")
                    license:expat)))) ; cJSON in the test suite
 
 (define-public mtpaint
-  (let ((commit "03b1b0938067b88d86d9f1b1088730f1934d411e")
-        (revision "1"))
   (package
     (name "mtpaint")
     ;; The author neither releases tarballs nor uses git version tags.
     ;; Instead, author puts version in git commit title.
-      (version (git-version "3.49.25" revision commit))
+    (version "3.49.25")
     (source
      (origin
        (method git-fetch)
        (uri (git-reference
-               (url "https://github.com/wjaguar/mtPaint/")
-               (commit commit)))
+             (url "https://github.com/wjaguar/mtPaint")
+             (commit "03b1b0938067b88d86d9f1b1088730f1934d411e")))
        (file-name (git-file-name name version))
        (sha256
         (base32 "0izm2wvj26566fd8mqvypr7bmv7jnq8qhp4760m7z2wrc4y8pjn1"))))
@@ -2107,17 +2105,13 @@ AOM, including with alpha.")
        ("lcms" ,lcms)
        ("zlib", zlib)
        ("glib" ,glib)
-         ;; support for gtk3 is in testing stage
+       ;; Support for gtk3 is in the testing stage.
        ("gtk+" ,gtk+-2)))
     (arguments
      `(#:configure-flags
-         (list
-          ;; internationalized version
-          "intl"
-          ;; install man page
-          "man")
-         ;; no check target
-         #:tests? #f))
+       (list "intl"                     ; build internationalized version
+             "man")                     ; build the man page
+       #:tests? #f))                    ; no test suite
     (home-page "http://mtpaint.sourceforge.net/")
     (synopsis "Create pixel art and manipulate digital images")
     (description
@@ -2125,4 +2119,4 @@ AOM, including with alpha.")
 It can create and edit indexed palette or 24bit RGB images, offers basic
 painting and palette manipulation tools.  It also handles JPEG, JPEG2000,
 GIF, TIFF, WEBP, BMP, PNG, XPM formats.")
-      (license license:gpl3+))))
+    (license license:gpl3+)))