git-gui: Refactor branch switch to support detached head

This is a major rewrite of the way we perform switching between
branches and the subsequent update of the working directory.  Like
core Git we now use a single code path to perform all changes: our
new checkout_op class.  We also use it for branch creation/update
as it integrates the tracking branch fetch process along with a
very basic merge (fast-forward and reset only currently).

Because some users have literally hundreds of local branches we
use the standard revision picker (with its branch filtering tool)
to select the local branch, rather than keeping all of the local
branches in the Branch menu.  The branch menu listing out all of
the available branches is simply not sane for those types of huge
repositories.

Users can now checkout a detached head by ticking off the option
in the checkout dialog.  This option is off by default for the
obvious reason, but it can be easily enabled for any local branch
by simply checking it.  We also detach the head if any non local
branch was selected, or if a revision expression was entered.

Signed-off-by: Shawn O. Pearce <spearce@spearce.org>

1 files changed, 88 insertions, 0 deletions

diff --git a/lib/branch_checkout.tcl b/lib/branch_checkout.tcl
new file mode 100644
index 0000000000..62230efe43
--- /dev/null
+++ b/lib/branch_checkout.tcl
@@ -0,0 +1,88 @@
+# git-gui branch checkout support
+# Copyright (C) 2007 Shawn Pearce
+
+class branch_checkout {
+
+field w              ; # widget path
+field w_rev          ; # mega-widget to pick the initial revision
+
+field opt_fetch     1; # refetch tracking branch if used?
+field opt_detach    0; # force a detached head case?
+
+constructor dialog {} {
+	make_toplevel top w
+	wm title $top "[appname] ([reponame]): Checkout Branch"
+	if {$top ne {.}} {
+		wm geometry $top "+[winfo rootx .]+[winfo rooty .]"
+	}
+
+	label $w.header -text {Checkout Branch} -font font_uibold
+	pack $w.header -side top -fill x
+
+	frame $w.buttons
+	button $w.buttons.create -text Checkout \
+		-default active \
+		-command [cb _checkout]
+	pack $w.buttons.create -side right
+	button $w.buttons.cancel -text {Cancel} \
+		-command [list destroy $w]
+	pack $w.buttons.cancel -side right -padx 5
+	pack $w.buttons -side bottom -fill x -pady 10 -padx 10
+
+	set w_rev [::choose_rev::new $w.rev {Revision}]
+	pack $w.rev -anchor nw -fill both -expand 1 -pady 5 -padx 5
+
+	labelframe $w.options -text {Options}
+
+	checkbutton $w.options.fetch \
+		-text {Fetch Tracking Branch} \
+		-variable @opt_fetch
+	pack $w.options.fetch -anchor nw
+
+	checkbutton $w.options.detach \
+		-text {Detach From Local Branch} \
+		-variable @opt_detach
+	pack $w.options.detach -anchor nw
+
+	pack $w.options -anchor nw -fill x -pady 5 -padx 5
+
+	bind $w <Visibility> [cb _visible]
+	bind $w <Key-Escape> [list destroy $w]
+	bind $w <Key-Return> [cb _checkout]\;break
+	tkwait window $w
+}
+
+method _checkout {} {
+	set spec [$w_rev get_tracking_branch]
+	if {$spec ne {} && $opt_fetch} {
+		set new {}
+	} elseif {[catch {set new [$w_rev commit_or_die]}]} {
+		return
+	}
+
+	if {$opt_detach} {
+		set ref {}
+	} else {
+		set ref [$w_rev get_local_branch]
+	}
+
+	set co [::checkout_op::new [$w_rev get] $new $ref]
+	$co parent $w
+	$co enable_checkout 1
+	if {$spec ne {} && $opt_fetch} {
+		$co enable_fetch $spec
+	}
+
+	if {[$co run]} {
+		destroy $w
+	} else {
+		$w_rev focus_filter
+	}
+}
+
+method _visible {} {
+	grab $w
+	$w_rev focus_filter
+}
+
+}