git: Infer changes by root commit correctly.

* tissue/git.scm (commit-deltas): Rename to ...
(commit-file-changes): ... this. Return list of pairs mapping old
files to new files.
(file-modification-table): Use commit-file-changes instead of
commit-deltas. Adapt to new return value.
* tests/git.scm: New file.
* .dir-locals.el (scheme-mode): Set scheme-indent-function for
with-variable and with-variables.

1 files changed, 26 insertions, 25 deletions

diff --git a/tissue/git.scm b/tissue/git.scm
index c837da7..562e715 100644
--- a/tissue/git.scm
+++ b/tissue/git.scm
@@ -1,5 +1,5 @@
 ;;; tissue --- Text based issue tracker
-;;; Copyright © 2022 Arun Isaac <arunisaac@systemreboot.net>
+;;; Copyright © 2022, 2023 Arun Isaac <arunisaac@systemreboot.net>
 ;;;
 ;;; This file is part of tissue.
 ;;;
@@ -152,9 +152,10 @@ to a file on the filesystem or in REPOSITORY."
           (call-with-port (open-bytevector-input-port (blob-content blob))
             proc)))))
 
-(define (commit-deltas repository commit)
-  "Return the list of <diff-delta> objects created by COMMIT with
-respect to its first parent in REPOSITORY."
+(define (commit-file-changes repository commit)
+  "Return a list of pairs describing files modified by COMMIT with
+respect to its first parent in REPOSITORY. Each pair maps the old
+filename before COMMIT to the new filename after COMMIT."
   (match (commit-parents commit)
     ((parent _ ...)
      (let ((diff (diff-tree-to-tree repository
@@ -162,7 +163,9 @@ respect to its first parent in REPOSITORY."
                                     (commit-tree commit))))
        (diff-find-similar! diff)
        (diff-fold (lambda (delta progress result)
-                    (cons delta result))
+                    (cons (cons (diff-file-path (diff-delta-old-file delta))
+                                (diff-file-path (diff-delta-new-file delta)))
+                          result))
                   (lambda (delta binary result)
                     result)
                   (lambda (delta hunk result)
@@ -171,7 +174,9 @@ respect to its first parent in REPOSITORY."
                     result)
                   (list)
                   diff)))
-    (() (list))))
+    (() (map (lambda (file)
+               (cons file file))
+             (tree-list (commit-tree commit))))))
 
 (define (file-modification-table repository)
   "Return a hashtable mapping files to the list of commits in REPOSITORY
@@ -180,25 +185,21 @@ that modified them."
         (renames (make-hashtable string-hash string=?)))
     (fold-commits
      (lambda (commit _)
-       (map (lambda (delta)
-              ;; Map old filename to current filename if they are
-              ;; different. Note that this manner of following renames
-              ;; requires a linear git history and will not work with
-              ;; branch merges.
-              (unless (string=? (diff-file-path (diff-delta-old-file delta))
-                                (diff-file-path (diff-delta-new-file delta)))
-                (hashtable-set! renames
-                                (diff-file-path (diff-delta-old-file delta))
-                                (diff-file-path (diff-delta-new-file delta))))
-              (hashtable-update! result
-                                 ;; If necessary, translate old
-                                 ;; filename to current filename.
-                                 (hashtable-ref renames
-                                                (diff-file-path (diff-delta-old-file delta))
-                                                (diff-file-path (diff-delta-old-file delta)))
-                                 (cut cons commit <>)
-                                 (list)))
-            (commit-deltas repository commit)))
+       (map (match-lambda
+              ((old-file . new-file)
+               ;; Map old filename to current filename if they are
+               ;; different. Note that this manner of following renames
+               ;; requires a linear git history and will not work with
+               ;; branch merges.
+               (unless (string=? old-file new-file)
+                 (hashtable-set! renames old-file new-file))
+               (hashtable-update! result
+                                  ;; If necessary, translate old
+                                  ;; filename to current filename.
+                                  (hashtable-ref renames old-file old-file)
+                                  (cut cons commit <>)
+                                  (list))))
+            (commit-file-changes repository commit)))
      #f
      repository)
     result))