Am 28.01.26 um 00:26 schrieb Junio C Hamano:

It is clear that "apply_tab_size 0" is designed for a single-parent
diff, while "apply_tab_size 1" is designed for two parents diff.  If
this new series to make sense, I think it should argue why that
setting that users are already familiar with for the past 14 years
is wrong, and "apply_tab_size 1" is more appropriate for a single
parent diff (and presumably "apply_tab_size 2" is better for two
aprent diff), I think.

I concur. Also, "apply_tab_size 0" is needed when the contents of an
unstaged file are shown instead of patch text.

+proc apply_tab_size {{firsttab {}}} {
+	global have_tk85 repo_config ui_diff
+
+	set w [font measure font_diff "0"]
+	if {$have_tk85 && $firsttab != 0} {
+		$ui_diff configure -tabs [list [expr {$firsttab * $w}] [expr {($firsttab + $repo_config(gui.tabsize)) * $w}]]

I think that these values for tabstops aren't optimal. It does not make
sense to have tabstop at column 1 for diff output, because there is
always at least one character ('+', '-', or SP), so that the first tab
would jump right to the second stop. In Gitk, the initial version looked
like this as well, but it this was changed soon after.

+	} elseif {$have_tk85 || $repo_config(gui.tabsize) != 8} {
+		$ui_diff configure -tabs [expr {$repo_config(gui.tabsize) * $w}]
+	} else {
+		$ui_diff configure -tabs {}
+	}
+}

-- Hannes