+if {![regexp {^[1-9]+(\.[0-9]+)+$} $_git_version]} {
+ catch {wm withdraw .}
+ if {[tk_messageBox \
+ -icon warning \
+ -type yesno \
+ -default no \
+ -title "[appname]: warning" \
+ -message "Git version cannot be determined.
+
+$_git claims it is version '$_real_git_version'.
+
+[appname] requires at least Git 1.5.0 or later.
+
+Assume '$_real_git_version' is version 1.5.0?
+"] eq {yes}} {
+ set _git_version 1.5.0
+ } else {
+ exit 1
+ }
+}
+unset _real_git_version
+