Subject: [PATCH v4] gitk: add external diff file rename detection

From: "ToBoMi via GitGitGadget" <[email-masked]>
Date: Mon, 28 Apr 2025 08:47:17 +0000

From: Tobias Boesch <[email-masked]>

If a file is renamed between commits and an external diff is started
through gitk on the original or the renamed file name,
gitk is unable to open the renamed file in the external diff editor.
It fails to fetch the renamed file from git, because it fetches it
using its original path in contrast to using the renamed path of the
file.
Detect the rename and open the external diff with the original and
the renamed file instead of no file (fetch the renamed file path and
name from git) no matter if the original or the renamed file is
selected in gitk.
Since moved or renamed file are handled the same way do this also
for moved files.

Signed-off-by: Tobias Boesch <[email-masked]>
---
    gitk: add external diff file rename detection
    
    Changes since v1:
    
     * Commit message ident
     * Commit message line length
    
    Changes since v2:
    
     * Removed option for rename detection (Adding GUI options seems to be
       not desired - which is understandable)
     * Rebased on current master of git-for-windows
     * Renamed variables for a better understanding
     * Made rename detection also work when the renamed file is selected in
       gitk
    
    Changes since v3:
    
     * Changed message to use present tense, removed bullet points and
       described changes in imperative mood

Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-1774%2FToBoMi%2Fdetect_renamed_files_when_opening_diff-v4
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-1774/ToBoMi/detect_renamed_files_when_opening_diff-v4
Pull-Request: https://github.com/gitgitgadget/git/pull/1774

Range-diff vs v3:

 1:  1a64e989713 ! 1:  948b94bef5c gitk: added external diff file rename detection
     @@ Metadata
      Author: Tobias Boesch <[email-masked]>
      
       ## Commit message ##
     -    gitk: added external diff file rename detection
     +    gitk: add external diff file rename detection
      
     -    * If a file was renamed between commits and an external diff is started
     -      through gitk on the original or the renamed file name,
     -      gitk was unable to open the renamed file in the external diff editor.
     -      It failed to fetch the renamed file from git, because it fetched it
     -      using its original path in contrast to using the renamed path of the
     -      file.
     -    * With this change gitk detects the rename and opens the external diff
     -      with the original and the renamed file instead of no file (it is able
     -      to fetch the renamed file path and name now from git).
     -    * Since git doesn't destinguish between move or rename this also works
     -      for moved files.
     -    * Showing the external diff with the original and the renamed file
     -      works when either of the files is selected in gitk.
     +    If a file is renamed between commits and an external diff is started
     +    through gitk on the original or the renamed file name,
     +    gitk is unable to open the renamed file in the external diff editor.
     +    It fails to fetch the renamed file from git, because it fetches it
     +    using its original path in contrast to using the renamed path of the
     +    file.
     +    Detect the rename and open the external diff with the original and
     +    the renamed file instead of no file (fetch the renamed file path and
     +    name from git) no matter if the original or the renamed file is
     +    selected in gitk.
     +    Since moved or renamed file are handled the same way do this also
     +    for moved files.
      
          Signed-off-by: Tobias Boesch <[email-masked]>

 gitk-git/gitk | 45 +++++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 43 insertions(+), 2 deletions(-)

diff --git a/gitk-git/gitk b/gitk-git/gitk
index bc9efa18566..ddbe60398f2 100755
--- a/gitk-git/gitk
+++ b/gitk-git/gitk
@@ -3806,6 +3806,39 @@ proc external_diff_get_one_file {diffid filename diffdir} {
                "revision $diffid"]
 }
 
+proc check_for_renames_in_diff {filepath} {
+    global ctext
+
+    set renamed_filenames [list {}]
+    set filename [file tail $filepath]
+    set rename_from_text_identifier_length 12
+    set rename_to_text_identifier_length 10
+    set reg_expr_rename_from {^rename from (.*$filename)}
+    set reg_expr_rename_from [subst -nobackslashes -nocommands $reg_expr_rename_from]
+    set rename_from_text_index [$ctext search -elide -regexp -- $reg_expr_rename_from 0.0]
+    if { ($rename_from_text_index != {})} {
+        set reg_expr_rename_to {^rename to (.*)}
+        set rename_to_text_index [$ctext search -elide -regexp -- $reg_expr_rename_to $rename_from_text_index]
+        if { ($rename_from_text_index != {}) && ($rename_to_text_index != {}) } {
+            lappend renamed_filenames [$ctext get "$rename_from_text_index + $rename_from_text_identifier_length chars" "$rename_from_text_index lineend"]
+            lappend renamed_filenames [$ctext get "$rename_to_text_index + $rename_to_text_identifier_length chars" "$rename_to_text_index lineend"]
+        }
+        return $renamed_filenames
+    }
+    set reg_expr_rename_to {^rename to (.*$filename)}
+    set reg_expr_rename_to [subst -nobackslashes -nocommands $reg_expr_rename_to]
+    set rename_to_text_index [$ctext search -elide -regexp -- $reg_expr_rename_to 0.0]
+    if { ($rename_to_text_index != {})} {
+        set reg_expr_rename_from {^rename from (.*)}
+        set rename_from_text_index [$ctext search -backwards -elide -regexp -- $reg_expr_rename_from $rename_to_text_index]
+        if { ($rename_to_text_index != {}) && ($rename_from_text_index != {}) } {
+            lappend renamed_filenames [$ctext get "$rename_from_text_index + $rename_from_text_identifier_length chars" "$rename_from_text_index lineend"]
+            lappend renamed_filenames [$ctext get "$rename_to_text_index + $rename_to_text_identifier_length chars" "$rename_to_text_index lineend"]
+        }
+        return $renamed_filenames
+    }
+}
+
 proc external_diff {} {
     global nullid nullid2
     global flist_menu_file
@@ -3836,8 +3869,16 @@ proc external_diff {} {
     if {$diffdir eq {}} return
 
     # gather files to diff
-    set difffromfile [external_diff_get_one_file $diffidfrom $flist_menu_file $diffdir]
-    set difftofile [external_diff_get_one_file $diffidto $flist_menu_file $diffdir]
+    set renamed_filenames [check_for_renames_in_diff $flist_menu_file]
+    set rename_from_filename [lindex $renamed_filenames 1]
+    set rename_to_filename [lindex $renamed_filenames 2]
+    if { ($rename_from_filename != {}) && ($rename_to_filename != {}) } {
+        set difffromfile [external_diff_get_one_file $diffidfrom $rename_from_filename $diffdir]
+        set difftofile [external_diff_get_one_file $diffidto $rename_to_filename $diffdir]
+    } else {
+        set difffromfile [external_diff_get_one_file $diffidfrom $flist_menu_file $diffdir]
+        set difftofile [external_diff_get_one_file $diffidto $flist_menu_file $diffdir]
+    }
 
     if {$difffromfile ne {} && $difftofile ne {}} {
         set cmd [list [shellsplit $extdifftool] $difffromfile $difftofile]

base-commit: 5b97a56fa0e7d580dc8865b73107407c9b3f0eff
-- 
gitgitgadget