Merge branch 'py/revert-hunks-lines'

git-gui learned to revert selected lines and hunks, just like it can
stage selected lines and hunks. To provide a safety net for accidental
revert, the most recent revert can be undone.

* py/revert-hunks-lines:
  git-gui: allow undoing last revert
  git-gui: return early when patch fails to apply
  git-gui: allow reverting selected hunk
  git-gui: allow reverting selected lines

Author: prati0100

git-gui.sh

@@ -1350,6 +1350,8 @@ set is_submodule_diff 0
 set is_conflict_diff 0
 set selected_commit_type new
 set diff_empty_count 0
+set last_revert {}
+set last_revert_enc {}
 
 set nullid "0000000000000000000000000000000000000000"
 set nullid2 "0000000000000000000000000000000000000001"
@@ -3604,15 +3606,31 @@ set ctxm .vpane.lower.diff.body.ctxm
 menu $ctxm -tearoff 0
 $ctxm add command \
 	-label [mc "Apply/Reverse Hunk"] \
-	-command {apply_hunk $cursorX $cursorY}
+	-command {apply_or_revert_hunk $cursorX $cursorY 0}
 set ui_diff_applyhunk [$ctxm index last]
 lappend diff_actions [list $ctxm entryconf $ui_diff_applyhunk -state]
 $ctxm add command \
 	-label [mc "Apply/Reverse Line"] \
-	-command {apply_range_or_line $cursorX $cursorY; do_rescan}
+	-command {apply_or_revert_range_or_line $cursorX $cursorY 0; do_rescan}
 set ui_diff_applyline [$ctxm index last]
 lappend diff_actions [list $ctxm entryconf $ui_diff_applyline -state]
 $ctxm add separator
+$ctxm add command \
+	-label [mc "Revert Hunk"] \
+	-command {apply_or_revert_hunk $cursorX $cursorY 1}
+set ui_diff_reverthunk [$ctxm index last]
+lappend diff_actions [list $ctxm entryconf $ui_diff_reverthunk -state]
+$ctxm add command \
+	-label [mc "Revert Line"] \
+	-command {apply_or_revert_range_or_line $cursorX $cursorY 1; do_rescan}
+set ui_diff_revertline [$ctxm index last]
+lappend diff_actions [list $ctxm entryconf $ui_diff_revertline -state]
+$ctxm add command \
+	-label [mc "Undo Last Revert"] \
+	-command {undo_last_revert; do_rescan}
+set ui_diff_undorevert [$ctxm index last]
+lappend diff_actions [list $ctxm entryconf $ui_diff_undorevert -state]
+$ctxm add separator
 $ctxm add command \
 	-label [mc "Show Less Context"] \
 	-command show_less_context
@@ -3691,7 +3709,7 @@ proc has_textconv {path} {
 }
 
 proc popup_diff_menu {ctxm ctxmmg ctxmsm x y X Y} {
-	global current_diff_path file_states
+	global current_diff_path file_states last_revert
 	set ::cursorX $x
 	set ::cursorY $y
 	if {[info exists file_states($current_diff_path)]} {
@@ -3705,19 +3723,28 @@ proc popup_diff_menu {ctxm ctxmmg ctxmsm x y X Y} {
 		tk_popup $ctxmsm $X $Y
 	} else {
 		set has_range [expr {[$::ui_diff tag nextrange sel 0.0] != {}}]
+		set u [mc "Undo Last Revert"]
 		if {$::ui_index eq $::current_diff_side} {
 			set l [mc "Unstage Hunk From Commit"]
+			set h [mc "Revert Hunk"]
+
 			if {$has_range} {
 				set t [mc "Unstage Lines From Commit"]
+				set r [mc "Revert Lines"]
 			} else {
 				set t [mc "Unstage Line From Commit"]
+				set r [mc "Revert Line"]
 			}
 		} else {
 			set l [mc "Stage Hunk For Commit"]
+			set h [mc "Revert Hunk"]
+
 			if {$has_range} {
 				set t [mc "Stage Lines For Commit"]
+				set r [mc "Revert Lines"]
 			} else {
 				set t [mc "Stage Line For Commit"]
+				set r [mc "Revert Line"]
 			}
 		}
 		if {$::is_3way_diff
@@ -3728,11 +3755,35 @@ proc popup_diff_menu {ctxm ctxmmg ctxmsm x y X Y} {
 			|| [string match {T?} $state]
 			|| [has_textconv $current_diff_path]} {
 			set s disabled
+			set revert_state disabled
 		} else {
 			set s normal
+
+			# Only allow reverting changes in the working tree. If
+			# the user wants to revert changes in the index, they
+			# need to unstage those first.
+			if {$::ui_workdir eq $::current_diff_side} {
+				set revert_state normal
+			} else {
+				set revert_state disabled
+			}
 		}
+
+		if {$last_revert eq {}} {
+			set undo_state disabled
+		} else {
+			set undo_state normal
+		}
+
 		$ctxm entryconf $::ui_diff_applyhunk -state $s -label $l
 		$ctxm entryconf $::ui_diff_applyline -state $s -label $t
+		$ctxm entryconf $::ui_diff_revertline -state $revert_state \
+			-label $r
+		$ctxm entryconf $::ui_diff_reverthunk -state $revert_state \
+			-label $h
+		$ctxm entryconf $::ui_diff_undorevert -state $undo_state \
+			-label $u
+
 		tk_popup $ctxm $X $Y
 	}
 }

lib/diff.tcl

@@ -55,7 +55,7 @@ proc reshow_diff {{after {}}} {
 
 proc force_diff_encoding {enc} {
 	global current_diff_path
-	
+
 	if {$current_diff_path ne {}} {
 		force_path_encoding $current_diff_path $enc
 		reshow_diff
@@ -567,24 +567,31 @@ proc read_diff {fd conflict_size cont_info} {
 	}
 }
 
-proc apply_hunk {x y} {
+proc apply_or_revert_hunk {x y revert} {
 	global current_diff_path current_diff_header current_diff_side
-	global ui_diff ui_index file_states
+	global ui_diff ui_index file_states last_revert last_revert_enc
 
 	if {$current_diff_path eq {} || $current_diff_header eq {}} return
 	if {![lock_index apply_hunk]} return
 
-	set apply_cmd {apply --cached --whitespace=nowarn}
+	set apply_cmd {apply --whitespace=nowarn}
 	set mi [lindex $file_states($current_diff_path) 0]
 	if {$current_diff_side eq $ui_index} {
 		set failed_msg [mc "Failed to unstage selected hunk."]
-		lappend apply_cmd --reverse
+		lappend apply_cmd --reverse --cached
 		if {[string index $mi 0] ne {M}} {
 			unlock_index
 			return
 		}
 	} else {
-		set failed_msg [mc "Failed to stage selected hunk."]
+		if {$revert} {
+			set failed_msg [mc "Failed to revert selected hunk."]
+			lappend apply_cmd --reverse
+		} else {
+			set failed_msg [mc "Failed to stage selected hunk."]
+			lappend apply_cmd --cached
+		}
+
 		if {[string index $mi 1] ne {M}} {
 			unlock_index
 			return
@@ -603,29 +610,40 @@ proc apply_hunk {x y} {
 		set e_lno end
 	}
 
+	set wholepatch "$current_diff_header[$ui_diff get $s_lno $e_lno]"
+
 	if {[catch {
 		set enc [get_path_encoding $current_diff_path]
 		set p [eval git_write $apply_cmd]
 		fconfigure $p -translation binary -encoding $enc
-		puts -nonewline $p $current_diff_header
-		puts -nonewline $p [$ui_diff get $s_lno $e_lno]
+		puts -nonewline $p $wholepatch
 		close $p} err]} {
 		error_popup "$failed_msg\n\n$err"
 		unlock_index
 		return
 	}
 
+	if {$revert} {
+		# Save a copy of this patch for undoing reverts.
+		set last_revert $wholepatch
+		set last_revert_enc $enc
+	}
+
 	$ui_diff conf -state normal
 	$ui_diff delete $s_lno $e_lno
 	$ui_diff conf -state disabled
 
+	# Check if the hunk was the last one in the file.
 	if {[$ui_diff get 1.0 end] eq "\n"} {
 		set o _
 	} else {
 		set o ?
 	}
 
-	if {$current_diff_side eq $ui_index} {
+	# Update the status flags.
+	if {$revert} {
+		set mi [string index $mi 0]$o
+	} elseif {$current_diff_side eq $ui_index} {
 		set mi ${o}M
 	} elseif {[string index $mi 0] eq {_}} {
 		set mi M$o
@@ -640,9 +658,9 @@ proc apply_hunk {x y} {
 	}
 }
 
-proc apply_range_or_line {x y} {
+proc apply_or_revert_range_or_line {x y revert} {
 	global current_diff_path current_diff_header current_diff_side
-	global ui_diff ui_index file_states
+	global ui_diff ui_index file_states last_revert
 
 	set selected [$ui_diff tag nextrange sel 0.0]
 
@@ -660,19 +678,27 @@ proc apply_range_or_line {x y} {
 	if {$current_diff_path eq {} || $current_diff_header eq {}} return
 	if {![lock_index apply_hunk]} return
 
-	set apply_cmd {apply --cached --whitespace=nowarn}
+	set apply_cmd {apply --whitespace=nowarn}
 	set mi [lindex $file_states($current_diff_path) 0]
 	if {$current_diff_side eq $ui_index} {
 		set failed_msg [mc "Failed to unstage selected line."]
 		set to_context {+}
-		lappend apply_cmd --reverse
+		lappend apply_cmd --reverse --cached
 		if {[string index $mi 0] ne {M}} {
 			unlock_index
 			return
 		}
 	} else {
-		set failed_msg [mc "Failed to stage selected line."]
-		set to_context {-}
+		if {$revert} {
+			set failed_msg [mc "Failed to revert selected line."]
+			set to_context {+}
+			lappend apply_cmd --reverse
+		} else {
+			set failed_msg [mc "Failed to stage selected line."]
+			set to_context {-}
+			lappend apply_cmd --cached
+		}
+
 		if {[string index $mi 1] ne {M}} {
 			unlock_index
 			return
@@ -829,7 +855,47 @@ proc apply_range_or_line {x y} {
 		puts -nonewline $p $wholepatch
 		close $p} err]} {
 		error_popup "$failed_msg\n\n$err"
+		unlock_index
+		return
+	}
+
+	if {$revert} {
+		# Save a copy of this patch for undoing reverts.
+		set last_revert $current_diff_header$wholepatch
+		set last_revert_enc $enc
 	}
 
 	unlock_index
 }
+
+# Undo the last line/hunk reverted. When hunks and lines are reverted, a copy
+# of the diff applied is saved. Re-apply that diff to undo the revert.
+#
+# Right now, we only use a single variable to hold the copy, and not a
+# stack/deque for simplicity, so multiple undos are not possible. Maybe this
+# can be added if the need for something like this is felt in the future.
+proc undo_last_revert {} {
+	global last_revert current_diff_path current_diff_header
+	global last_revert_enc
+
+	if {$last_revert eq {}} return
+	if {![lock_index apply_hunk]} return
+
+	set apply_cmd {apply --whitespace=nowarn}
+	set failed_msg [mc "Failed to undo last revert."]
+
+	if {[catch {
+		set enc $last_revert_enc
+		set p [eval git_write $apply_cmd]
+		fconfigure $p -translation binary -encoding $enc
+		puts -nonewline $p $last_revert
+		close $p} err]} {
+		error_popup "$failed_msg\n\n$err"
+		unlock_index
+		return
+	}
+
+	set last_revert {}
+
+	unlock_index
+}