gitk: support auto-copy comit ID to primary clipboard

Auto-select ("Copy commit ID to X11 selection") is useful when a
selection cliboard exists, but otherwise generally meaningless, for
instance on Windows.

Add a similar pref and behavior which copies the commit ID to the
primary clipboard - for platforms without a selection clipboard, but
which can also be useful additionally on platforms with selection.

Note that while autoselect is enabled by default, autocopy isn't.

That's because the selection clipboard is typically dispensable, while
the primary clipboard can be considered a more precious resource,
which we don't want to (clear and) overwrite by default.

Signed-off-by: Avi Halachmi (:avih) <avihpit@yahoo.com>

gitk

@@ -7344,7 +7344,7 @@ proc selectline {l isnew {desired_loc {}} {switch_to_patch 0}} {
     global mergemax numcommits pending_select
     global cmitmode showneartags allcommits
     global targetrow targetid lastscrollrows
-    global autoselect autosellen jump_to_here
+    global autocopy autoselect autosellen jump_to_here
     global vinlinediff
 
     unset -nocomplain pending_select
@@ -7413,6 +7413,10 @@ proc selectline {l isnew {desired_loc {}} {switch_to_patch 0}} {
     if {$autoselect} {
         $sha1entry selection range 0 $autosellen
     }
+    if {$autocopy} {
+        clipboard clear
+        clipboard append [string range $id 0 [expr $autosellen - 1]]
+    }
     rhighlight_sel $id
 
     $ctext conf -state normal
@@ -11576,7 +11580,7 @@ proc create_prefs_page {w} {
 
 proc prefspage_general {notebook} {
     global NS maxwidth maxgraphpct showneartags showlocalchanges
-    global tabstop limitdiffs autoselect autosellen extdifftool perfile_attrs
+    global tabstop limitdiffs autocopy autoselect autosellen extdifftool perfile_attrs
     global hideremotes want_ttk have_ttk maxrefs web_browser
 
     set page [create_prefs_page $notebook.general]
@@ -11598,6 +11602,9 @@ proc prefspage_general {notebook} {
         -variable hideremotes
     grid x $page.hideremotes -sticky w
 
+    ${NS}::checkbutton $page.autocopy -text [mc "Copy commit ID to clipboard"] \
+        -variable autocopy
+    grid x $page.autocopy -sticky w
     ${NS}::checkbutton $page.autoselect -text [mc "Copy commit ID to X11 selection"] \
         -variable autoselect
     grid x $page.autoselect -sticky w
@@ -12403,6 +12410,7 @@ set maxlinelen 200
 set showlocalchanges 1
 set limitdiffs 1
 set datetimeformat "%Y-%m-%d %H:%M:%S"
+set autocopy 0
 set autoselect 1
 set autosellen 40
 set perfile_attrs 0
@@ -12500,7 +12508,7 @@ config_check_tmp_exists 50
 
 set config_variables {
     mainfont textfont uifont tabstop findmergefiles maxgraphpct maxwidth
-    cmitmode wrapcomment autoselect autosellen showneartags maxrefs visiblerefs
+    cmitmode wrapcomment autocopy autoselect autosellen showneartags maxrefs visiblerefs
     hideremotes showlocalchanges datetimeformat limitdiffs uicolor want_ttk
     bgcolor fgcolor uifgcolor uifgdisabledcolor colors diffcolors mergecolors
     markbgcolor diffcontext selectbgcolor foundbgcolor currentsearchhitbgcolor