git-gui: Support resolving conflicts via the diff context menu.

If the file has merge conflicts, show a special version of the
diff context menu, which includes conflict resolution commands
instead of Stage Hunk/Line. This patch only supports resolving
by discarding all sides except one.

Discarding is the only way to resolve conflicts involving symlinks
and/or deletion, excluding manual editing.

Signed-off-by: Alexander Gavrilov <angavrilov@gmail.com>
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>

1 files changed, 98 insertions, 0 deletions

diff --git a/lib/mergetool.tcl b/lib/mergetool.tcl
new file mode 100644
index 0000000000..7945d746f8
--- /dev/null
+++ b/lib/mergetool.tcl
@@ -0,0 +1,98 @@
+# git-gui merge conflict resolution
+# parts based on git-mergetool (c) 2006 Theodore Y. Ts'o
+
+proc merge_resolve_one {stage} {
+	global current_diff_path
+
+	switch -- $stage {
+		1 { set target [mc "the base version"] }
+		2 { set target [mc "this branch"] }
+		3 { set target [mc "the other branch"] }
+	}
+
+	set op_question [mc "Force resolution to %s?
+Note that the diff shows only conflicting changes.
+
+%s will be overwritten.
+
+This operation can be undone only by restarting the merge." \
+		$target [short_path $current_diff_path]]
+
+	if {[ask_popup $op_question] eq {yes}} {
+		merge_load_stages $current_diff_path [list merge_force_stage $stage]
+	}
+}
+
+proc merge_add_resolution {path} {
+	global current_diff_path
+
+	if {$path eq $current_diff_path} {
+		set after {reshow_diff;}
+	} else {
+		set after {}
+	}
+
+	update_index \
+		[mc "Adding resolution for %s" [short_path $path]] \
+		[list $path] \
+		[concat $after [list ui_ready]]
+}
+
+proc merge_force_stage {stage} {
+	global current_diff_path merge_stages
+
+	if {$merge_stages($stage) ne {}} {
+		git checkout-index -f --stage=$stage -- $current_diff_path
+	} else {
+		file delete -- $current_diff_path
+	}
+
+	merge_add_resolution $current_diff_path
+}
+
+proc merge_load_stages {path cont} {
+	global merge_stages_fd merge_stages merge_stages_buf
+
+	if {[info exists merge_stages_fd]} {
+		catch { kill_file_process $merge_stages_fd }
+		catch { close $merge_stages_fd }
+	}
+
+	set merge_stages(0) {}
+	set merge_stages(1) {}
+	set merge_stages(2) {}
+	set merge_stages(3) {}
+	set merge_stages_buf {}
+
+	set merge_stages_fd [eval git_read ls-files -u -z -- $path]
+
+	fconfigure $merge_stages_fd -blocking 0 -translation binary -encoding binary
+	fileevent $merge_stages_fd readable [list read_merge_stages $merge_stages_fd $cont]
+}
+
+proc read_merge_stages {fd cont} {
+	global merge_stages_buf merge_stages_fd merge_stages
+
+	append merge_stages_buf [read $fd]
+	set pck [split $merge_stages_buf "\0"]
+	set merge_stages_buf [lindex $pck end]
+
+	if {[eof $fd] && $merge_stages_buf ne {}} {
+		lappend pck {}
+		set merge_stages_buf {}
+	}
+
+	foreach p [lrange $pck 0 end-1] {
+		set fcols [split $p "\t"]
+		set cols  [split [lindex $fcols 0] " "]
+		set stage [lindex $cols 2]
+		
+		set merge_stages($stage) [lrange $cols 0 1]
+	}
+
+	if {[eof $fd]} {
+		close $fd
+		unset merge_stages_fd
+		eval $cont
+	}
+}