Cleaned up the code. added some documentation.

main.rkt

@@ -28,6 +28,10 @@
 (define git-commands (make-hash))
 
 
+;; goal: Invoke a supported Git command through the command table.
+;; pre: command is a registered Git command symbol.
+;; post: The selected command has processed all supplied arguments.
+;; result: The command-specific result.
 (define-syntax git
   (syntax-rules ()
     ((_ command b1 ...)
@@ -51,6 +55,27 @@
         (g args)
         (g (cons '--porcelain args)))))
 
+(define (status->symbol status)
+  (cond
+    ((string=? status " ") 'unchanged)
+    ((string=? status "M") 'modified)
+    ((string=? status "T") 'type-changed)
+    ((string=? status "A") 'added)
+    ((string=? status "D") 'deleted)
+    ((string=? status "R") 'renamed)
+    ((string=? status "C") 'copied)
+    ((string=? status "U") 'unmerged)
+    ((string=? status "?") 'untracked)
+    ((string=? status "!") 'ignored)
+    (else (error 'git-status "Unexpected status: ~a" status))))
+
+(define (nothing-to-commit? out)
+  (ormap (λ (line)
+           (let ((line* (string-downcase line)))
+             (or (string-contains? line* "nothing to commit")
+                 (string-contains? line* "no changes added to commit"))))
+         out))
+
 
 (define-syntax def-cmd
   (syntax-rules ()
@@ -68,37 +93,38 @@
     )
   )
 
+;; goal: Return the complete Git index and worktree status for every reported file.
+;; pre: The current directory is inside a Git working tree.
+;; post: Git status has been invoked with --porcelain.
+;; result: A list containing (index-status worktree-status file) for every file.
 (def-cmd git-status cmd-git-status 'status
   add-porcelain
   (λ (cmd exit-code result output out info)
     (dbg-git (format "~a" output))
     (if (= exit-code 0)
-        (if result
-            (map (λ (line)
-                   (let* ((state (string->symbol (string-trim (substring line 0 2))))
-                          (file (string-trim (substring line 3))))
-                     (cond
-                       ([eq? state '??] (list 'new file))
-                       ([eq? state 'M] (list 'modified file))
-                       ([eq? state 'A] (list 'added file))
-                       ([eq? state 'D] (list 'deleted file))
-                       ([eq? state 'AM] (list 'modified file))
-                       ([eq? state 'AD] (list 'deleted file))
-                       ([eq? state 'MM] (list 'modified file))
-                       ([eq? state 'MD] (list 'deleted file))
-                       (else
-                        (git-error 'status "Unexpected state" state))
-                       )
-                     ))
-                 out)
-            (git-error 'status "Error" output))
+        (map (λ (line)
+               (if (< (string-length line) 3)
+                   (git-error 'status "Unexpected output" line)
+                   (list (status->symbol (substring line 0 1))
+                         (status->symbol (substring line 1 2))
+                         (substring line 3))))
+             (map cadr
+                  (filter (λ (entry) (eq? (car entry) 'stdout)) output)))
         (git-error 'status "Exitcode <> 0" (cons (format "~a\n" exit-code) output))
         ))
   )
 
 
+;; goal: Add file contents to the Git index.
+;; pre: The supplied arguments are valid for git add.
+;; post: Git add has completed successfully or an exception has been raised.
+;; result: #t after a successful Git command.
 (def-cmd git-add cmd-git-add 'add)
 
+;; goal: Create a Git commit.
+;; pre: A commit message is supplied or can be requested from the user.
+;; post: The commit was created, nothing needed committing, or an exception was raised.
+;; result: #t after a commit or when the repository has nothing to commit.
 (def-cmd git-commit cmd-git-commit 'commit
   (λ (args info)
     (with-handlers ([exn:fail? (λ (e)
@@ -109,15 +135,32 @@
       (check-git-args 'commit args '((-m 1 "A commit message is mandatory")))))
   (λ (cmd exit-code result output out info)
     (cond
-      ((= exit-code 1) (git-displ out) #t)
+      ((and (= exit-code 1)
+            (nothing-to-commit? out))
+       (git-displ out)
+       #t)
       (else 
        (std-process-git-result cmd exit-code result output out info))))
   )
 
+;; goal: Push local changes to a remote repository.
+;; pre: The supplied arguments are valid for git push.
+;; post: Git push has completed successfully or an exception has been raised.
+;; result: #t after a successful push.
 (def-cmd git-push cmd-git-push 'push add-porcelain)
+
+;; goal: Fetch and integrate changes from a remote repository.
+;; pre: The supplied arguments are valid for git pull.
+;; post: Git pull has completed successfully or an exception has been raised.
+;; result: #t after a successful pull.
 (def-cmd git-pull cmd-git-pull 'pull)
 (def-cmd git-branch cmd-git-branch 'branch)
 (def-cmd git-clone cmd-git-clone 'clone)
+
+;; goal: Display the Git commit log.
+;; pre: The supplied arguments are valid for git log.
+;; post: Git log has completed successfully or an exception has been raised.
+;; result: #t after successfully displaying the log.
 (def-cmd git-log cmd-git-log 'log)
 (def-cmd git-rev-list cmd-git-rev-list 'rev-list)
 
@@ -129,6 +172,10 @@
 
 (hash-set! git-commands 'version cmd-git-version)
 
+;; goal: Increment the package version in info.rkt.
+;; pre: kind is 'maj, 'major, 'min, 'minor or 'patch.
+;; post: The version definition in info.rkt has been updated.
+;; result: The new version as a list containing major, minor and patch.
 (define (git-new-version . args)
   (cmd-git-new-version args))
 
@@ -153,8 +200,12 @@
                      "\n")))
           (diff->html diff)
           #t)
-        #f)))
+          #f)))
 
+;; goal: Search tracked files for a pattern.
+;; pre: The supplied arguments are valid for git grep.
+;; post: Git grep has completed; exit code one is treated as no matches.
+;; result: A list containing file, line number, match count and matched text.
 (def-cmd git-grep cmd-git-grep 'grep
   (λ (args info)
     (let ((matches #f)