gitk: Added external diff file rename detection

* If a file was renamed between commits and
    an external diff is started through gitk
    by selecting the FILE THAT IS renamed,
    gitk was unable to open the renamed file
    in the external diff editor (it failed
    to fetch the file from git, cause it
    fetched it with the wrong path)
*   gitk now detects the rename and opens the
    external diff with the renamed file instead
    of no file (it is able to fetch the renamed
    file now from git with the renamed
    path/filename)
* Since git doesn't destinguish between move or
    rename this also works for moved files
* External diff detection and usage is optional
    and has to be enabled in gitk settings
* External rename detection ist marked
    EXPERIMENTAL in the settings and disabled
    by default
* Showing the renamed file doesn't work when THE
    RENAMED FILE is selected in gitk and an
    external diff ist started on that file,
    because the selected file is not renamed in
    that commit. It already IS the renamed file.

gitk-git/gitk

@@ -3662,11 +3662,33 @@ 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 $filepath]
+    set rename_from_text_length 12
+    set rename_to_text_length 10
+    set reg_expr_rename_from {^rename from (.*$filename)}
+    set reg_expr_rename_from [subst -nobackslashes -nocommands $reg_expr_rename_from]
+    set reg_expr_rename_to {^rename to (.*)}
+    set rename_from_text_index [$ctext search -elide -regexp -- $reg_expr_rename_from 0.0]
+    if { ($rename_from_text_index != {})} {
+        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 + $rename_from_text_length chars" "$rename_from_text_index lineend"]
+            lappend renamed_filenames [$ctext get "$rename_to_text_index + $rename_to_text_length chars" "$rename_to_text_index lineend"]
+        }
+    }
+    return $renamed_filenames
+}
+
 proc external_diff {} {
     global nullid nullid2
     global flist_menu_file
     global diffids
     global extdifftool
+    global file_rename_detection
 
     if {[llength $diffids] == 1} {
         # no reference commit given
@@ -3692,8 +3714,21 @@ proc external_diff {} {
     if {$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 $diffdir]
+    if {$file_rename_detection} {
+        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]
+        }
+    } 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]
@@ -11577,7 +11612,7 @@ proc create_prefs_page {w} {
 proc prefspage_general {notebook} {
     global NS maxwidth maxgraphpct showneartags showlocalchanges
     global tabstop limitdiffs autoselect autosellen extdifftool perfile_attrs
-    global hideremotes want_ttk have_ttk maxrefs web_browser
+    global hideremotes want_ttk have_ttk maxrefs web_browser file_rename_detection
 
     set page [create_prefs_page $notebook.general]
 
@@ -11639,12 +11674,16 @@ proc prefspage_general {notebook} {
     grid $page.lgen - -sticky w -pady 10
     ${NS}::checkbutton $page.want_ttk -variable want_ttk \
         -text [mc "Use themed widgets"]
+    ${NS}::checkbutton $page.file_rename_detection -variable file_rename_detection \
+        -text [mc "Use ext diff file rename detection"]
+    ${NS}::label $page.file_rename_detection_note -text [mc "(EXPERIMENTAL\nTries to find the file path of a\nrenamed file in external diff)"]
     if {$have_ttk} {
         ${NS}::label $page.ttk_note -text [mc "(change requires restart)"]
     } else {
         ${NS}::label $page.ttk_note -text [mc "(currently unavailable)"]
     }
     grid x $page.want_ttk $page.ttk_note -sticky w
+    grid x $page.file_rename_detection $page.file_rename_detection_note -sticky w
     return $page
 }
 
@@ -11725,7 +11764,7 @@ proc doprefs {} {
     global oldprefs prefstop showneartags showlocalchanges
     global uicolor bgcolor fgcolor ctext diffcolors selectbgcolor markbgcolor
     global tabstop limitdiffs autoselect autosellen extdifftool perfile_attrs
-    global hideremotes want_ttk have_ttk
+    global hideremotes want_ttk have_ttk file_rename_detection
 
     set top .gitkprefs
     set prefstop $top
@@ -11734,7 +11773,7 @@ proc doprefs {} {
         return
     }
     foreach v {maxwidth maxgraphpct showneartags showlocalchanges \
-                   limitdiffs tabstop perfile_attrs hideremotes want_ttk} {
+                   limitdiffs tabstop perfile_attrs hideremotes want_ttk file_rename_detection} {
         set oldprefs($v) [set $v]
     }
     ttk_toplevel $top
@@ -11860,7 +11899,7 @@ proc prefscan {} {
     global oldprefs prefstop
 
     foreach v {maxwidth maxgraphpct showneartags showlocalchanges \
-                   limitdiffs tabstop perfile_attrs hideremotes want_ttk} {
+                   limitdiffs tabstop perfile_attrs hideremotes want_ttk file_rename_detection} {
         global $v
         set $v $oldprefs($v)
     }
@@ -12404,6 +12443,7 @@ set autoselect 1
 set autosellen 40
 set perfile_attrs 0
 set want_ttk 1
+set file_rename_detection 0
 
 if {[tk windowingsystem] eq "aqua"} {
     set extdifftool "opendiff"
@@ -12498,7 +12538,7 @@ config_check_tmp_exists 50
 set config_variables {
     mainfont textfont uifont tabstop findmergefiles maxgraphpct maxwidth
     cmitmode wrapcomment autoselect autosellen showneartags maxrefs visiblerefs
-    hideremotes showlocalchanges datetimeformat limitdiffs uicolor want_ttk
+    hideremotes showlocalchanges datetimeformat limitdiffs uicolor want_ttk file_rename_detection
     bgcolor fgcolor uifgcolor uifgdisabledcolor colors diffcolors mergecolors
     markbgcolor diffcontext selectbgcolor foundbgcolor currentsearchhitbgcolor
     extdifftool perfile_attrs headbgcolor headfgcolor headoutlinecolor