Merge branch 'three-way-diff' into 'master'

pacdiff: add option to view diffs in 3-way fashion

See merge request pacman/pacman-contrib!18

4 files changed, 67 insertions, 9 deletions

diff --git a/CHANGES.md b/CHANGES.md
index 3b0a41c..155df4a 100644
--- a/CHANGES.md
+++ b/CHANGES.md
@@ -8,6 +8,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 ### Added
 - zsh completions (!14)
 - pacdiff: Add backup option to save old files (.bak) when (O)verwriting (!17)
+- pacdiff: Add -3/--threeway option to view diffs in 3-way fashion
 
 
 ## [1.5.3]
diff --git a/completions/zsh/_pacdiff b/completions/zsh/_pacdiff
index 1b5546e..2350731 100644
--- a/completions/zsh/_pacdiff
+++ b/completions/zsh/_pacdiff
@@ -14,6 +14,7 @@ args=(
 	'(-o --output)'{-o,--output}'[print files instead of merging them]'
 	'(-s --sudo)'{-s,--sudo}'[use sudo and sudoedit to merge/remove files]'
 	'(-b --backup)'{-b,--backup}'[when overwriting, save old files with .bak]'
+	'(-3 --threeway)'{-3,--threeway}'[view diffs in 3-way fashion]'
 	'(-)'{--help,-h}'[display help message]'
 	'(-)--version[display version]'
 )
diff --git a/doc/pacdiff.8.adoc b/doc/pacdiff.8.adoc
index cb291ac..189b0b0 100644
--- a/doc/pacdiff.8.adoc
+++ b/doc/pacdiff.8.adoc
@@ -56,6 +56,10 @@ Options
 *-b, \--backup*::
 	When overwriting, save old files with .bak.
 
+*-3, \--threeway*::
+	View diffs in 3-way fashion if the base package is available in the cache.
+    Fall back to regular 2-way diff otherwise.
+
 See Also
 --------
 linkman:pacman[8], linkman:pacman.conf[5]
diff --git a/src/pacdiff.sh.in b/src/pacdiff.sh.in
index 526ccf3..685b5a2 100644
--- a/src/pacdiff.sh.in
+++ b/src/pacdiff.sh.in
@@ -32,7 +32,7 @@ cachedir=
 USE_COLOR='y'
 SUDO=''
 declare -a oldsaves
-declare -i USE_FIND=0 USE_LOCATE=0 USE_PACDB=0 OUTPUTONLY=0 BACKUP=0
+declare -i USE_FIND=0 USE_LOCATE=0 USE_PACDB=0 OUTPUTONLY=0 BACKUP=0 THREE_WAY_DIFF=0
 
 # Import libmakepkg
 source "$LIBRARY"/util/message.sh
@@ -62,6 +62,7 @@ General Options:
                       (default: read from @sysconfdir@/pacman.conf)
   -s/--sudo           use sudo and sudoedit to merge/remove files
   -b/--backup         when overwriting, save old files with .bak
+  -3/--threeway       view diffs in 3-way fashion
 
 Environment Variables:
   DIFFPROG          override the merge program: (default: 'vim -d')
@@ -106,6 +107,62 @@ base_cache_tar() {
 	popd &>/dev/null
 }
 
+diffprog_fn() {
+	if [[ -n "$SUDO" ]]; then
+		SUDO_EDITOR="$diffprog" sudoedit "$@"
+	else
+		$diffprog "$@"
+	fi
+}
+
+view_diff() {
+	pacfile="$1"
+	file="$2"
+
+	package="$(pacman -Qoq "$file")" || return 1
+	base_tar="$(base_cache_tar "$package")"
+
+	two_way_diff() {
+		diffprog_fn "$pacfile" "$file"
+	}
+
+	three_way_diff() {
+		diffprog_fn "$pacfile" "$base" "$file"
+	}
+
+	unset tempdir
+
+	if (( ! THREE_WAY_DIFF )); then
+		two_way_diff
+	elif [[ -z $base_tar ]]; then
+		msg2 "Unable to find a base package. falling back to 2-way diff."
+		two_way_diff
+	else
+		basename="$(basename "$file")"
+		tempdir="$(mktemp -d --tmpdir "pacdiff-diff-$basename.XXX")"
+		base="$(mktemp "$tempdir"/"$basename.base.XXX")"
+		merged="$(mktemp "$tempdir"/"$basename.merged.XXX")"
+
+		if ! bsdtar -xqOf "$base_tar" "${file#/}" >"$base"; then
+			msg2 "Unable to extract the previous version of this file. falling back to 2-way diff."
+			two_way_diff
+		else
+			three_way_diff
+		fi
+	fi
+
+	ret=1
+
+	if cmp -s "$pacfile" "$file"; then
+		msg2 "Files are identical, removing..."
+		$SUDO rm -v "$pacfile"
+		ret=0
+	fi
+
+	$SUDO rm -rf "$tempdir"
+	return $ret
+}
+
 merge_file() {
 	pacfile="$1"
 	file="$2"
@@ -190,6 +247,8 @@ while [[ -n "$1" ]]; do
 			SUDO=sudo;;
 		-b|--backup)
 			BACKUP=1;;
+		-3|--threeway)
+			THREE_WAY_DIFF=1 ;;
 		-V|--version)
 			version; exit 0;;
 		-h|--help)
@@ -277,14 +336,7 @@ while IFS= read -u 3 -r -d '' pacfile; do
 					$SUDO mv -v "$pacfile" "$file"
 					break ;;
 				v|V)
-					if [[ -n "$SUDO" ]]; then
-						SUDO_EDITOR="$diffprog" sudoedit "$pacfile" "$file"
-					else
-						$diffprog "$pacfile" "$file"
-					fi
-					if cmp -s "$pacfile" "$file"; then
-						msg2 "Files are identical, removing..."
-						$SUDO rm -v "$pacfile"
+					if view_diff "$pacfile" "$file"; then
 						break
 					fi ;;
 				m|M)