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.

3 files changed, 88 insertions, 25 deletions

diff --git a/.dir-locals.el b/.dir-locals.el
index d129e76..f6bf9b6 100644
--- a/.dir-locals.el
+++ b/.dir-locals.el
@@ -11,6 +11,8 @@
   (eval . (put 'function-documentation 'scheme-indent-function 2))
   (eval . (put 'docstring-function-documentation 'scheme-indent-function 2))
   (eval . (put 'with-ellipsis 'scheme-indent-function 1))
+  (eval . (put 'with-variable 'scheme-indent-function 2))
+  (eval . (put 'with-variables 'scheme-indent-function 1))
   (eval . (font-lock-add-keywords 'scheme-mode
                                   (list (cons (rx "(" (group "define-lazy"))
                                               (list 1 'font-lock-keyword-face))
diff --git a/tests/git.scm b/tests/git.scm
new file mode 100644
index 0000000..bf2d9eb
--- /dev/null
+++ b/tests/git.scm
@@ -0,0 +1,60 @@
+;;; tissue --- Text based issue tracker
+;;; Copyright © 2023 Arun Isaac <arunisaac@systemreboot.net>
+;;;
+;;; This file is part of tissue.
+;;;
+;;; tissue is free software: you can redistribute it and/or modify it
+;;; under the terms of the GNU General Public License as published by
+;;; the Free Software Foundation, either version 3 of the License, or
+;;; (at your option) any later version.
+;;;
+;;; tissue is distributed in the hope that it will be useful, but
+;;; WITHOUT ANY WARRANTY; without even the implied warranty of
+;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+;;; General Public License for more details.
+;;;
+;;; You should have received a copy of the GNU General Public License
+;;; along with tissue.  If not, see <https://www.gnu.org/licenses/>.
+
+(import (srfi srfi-26)
+        (srfi srfi-64)
+        (ice-9 match))
+
+(define (with-variable variable value thunk)
+  "Set VARIABLE to VALUE, run THUNK and restore the old value of
+VARIABLE. Return the value returned by THUNK."
+  (let ((old-value (variable-ref variable)))
+    (dynamic-wind
+      (cut variable-set! variable value)
+      thunk
+      (cut variable-set! variable old-value))))
+
+(define (with-variables variable-bindings thunk)
+  "Set VARIABLE-BINDINGS, run THUNK and restore the old values of the
+variables. Return the value returned by THUNK. VARIABLE-BINDINGS is a
+list of pairs mapping variables to their values."
+  (match variable-bindings
+    (((variable . value) tail ...)
+     (with-variable variable value
+       (cut with-variables tail thunk)))
+    (() (thunk))))
+
+(define-syntax-rule (var@@ module-name variable-name)
+  (module-variable (resolve-module 'module-name)
+                   'variable-name))
+
+(test-begin "git")
+
+(test-equal "Infer changes by root commit"
+  '(("foo" . "foo")
+    ("bar" . "bar"))
+  (with-variables (list (cons (var@@ (git) commit-parents)
+                              (const (list)))
+                        (cons (var@@ (git) commit-tree)
+                              (const #t))
+                        (cons (var@@ (git) tree-list)
+                              (const (list "foo" "bar"))))
+    (cut (@@ (tissue git) commit-file-changes)
+         #f #f)))
+
+(test-end "git")
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))