lint: Add 'formatting' checker.

* guix/scripts/lint.scm (report-tabulations, report-trailing-white-space,
  report-long-line, report-formatting-issues, check-formatting): New
  procedures.
  (%formatting-reporters): New variable.
  (%checkers): Add 'formatting' checker.
* tests/lint.scm ("formatting: tabulation", "formatting: trailing white
  space", "formatting: long line", "formatting: alright"): New tests.
* doc/guix.texi (Invoking guix lint): Mention the 'formatting' checker.

1 files changed, 26 insertions, 0 deletions

diff --git a/tests/lint.scm b/tests/lint.scm
index 2807eba1cc..5d56420966 100644
--- a/tests/lint.scm
+++ b/tests/lint.scm
@@ -420,6 +420,32 @@ requests."
           (check-source pkg))))
     "not reachable: 404")))
 
+(test-assert "formatting: tabulation"
+  (string-contains
+   (with-warnings
+     (check-formatting (dummy-package "leave the tab here:	")))
+   "tabulation"))
+
+(test-assert "formatting: trailing white space"
+  (string-contains
+   (with-warnings
+     ;; Leave the trailing white space on the next line!
+     (check-formatting (dummy-package "x")))            
+   "trailing white space"))
+
+(test-assert "formatting: long line"
+  (string-contains
+   (with-warnings
+     (check-formatting
+      (dummy-package "x"                          ;here is a stupid comment just to make a long line
+                     )))
+   "too long"))
+
+(test-assert "formatting: alright"
+  (string-null?
+   (with-warnings
+     (check-formatting (dummy-package "x")))))
+
 (test-end "lint")