vlib,tools: add an arrays.diff module, implement a simple platform independent tool v diff file1.txt file2.txt using it (#24428)

vlib/arrays/diff/diff_test.v

@@ -0,0 +1,130 @@
+import arrays.diff
+
+fn test_diff_array() {
+	mut aa := ['hi', '1', '5', '3']
+	mut bb := aa.clone()
+	mut ctx := diff.diff(aa, bb)
+	assert ctx.changes.len == 0
+	bb.insert(2, 'max')
+	// aa := ['hi', '1', '5', '3']
+	// bb := ['hi', '1', 'max', '5', '3']
+	ctx = diff.diff(aa, bb)
+	assert ctx.changes == [
+		diff.DiffChange{
+			a:   2
+			b:   2
+			del: 0
+			ins: 1
+		},
+	]
+
+	bb.delete(4)
+	// aa := ['hi', '1', '5', '3']
+	// bb := ['hi', '1', 'max', '5']
+	ctx = diff.diff(aa, bb)
+	assert ctx.changes == [
+		diff.DiffChange{
+			a:   2
+			b:   2
+			del: 0
+			ins: 1
+		},
+		diff.DiffChange{
+			a:   3
+			b:   4
+			del: 1
+			ins: 0
+		},
+	]
+
+	str1 := ctx.generate_patch()
+	assert str1 == 'hi
+1
+-5
+-3
++max
++5
+'
+
+	str2 := ctx.generate_patch(block_header: true)
+	assert str2 == '@@ -1,7 +1,7 @@
+hi
+1
+-5
+-3
++max
++5
+'
+
+	str3 := ctx.generate_patch(block_header: true, unified: 1)
+	assert str3 == '@@ -2,4 +2,4 @@
+1
+-5
+-3
++max
++5
+'
+	str4 := ctx.generate_patch(block_header: true, unified: 10)
+	assert str4 == '@@ -1,14 +1,14 @@
+hi
+1
+-5
+-3
++max
++5
+'
+
+	str5 := ctx.generate_patch(block_header: true, unified: -1)
+	assert str5 == '@@ -3,2 +3,2 @@
+-5
+-3
++max
++5
+'
+}
+
+fn test_diff_runes() {
+	mut aa := 'brown fox jumps over the lazy dog'.runes()
+	mut bb := 'brwn faax junps ovver the lay daog'.runes()
+	mut ctx := diff.diff(aa, bb)
+
+	str1 := ctx.generate_patch()
+	assert str1 == 'b
+r
+-o
+w
+n
+ 
+f
+-o
++a
++a
+x
+ 
+j
+u
+-m
++n
+p
+s
+ 
+o
++v
+v
+e
+r
+ 
+l
+a
+-z
+-y
+- 
+-d
++y
++ 
++d
++a
+o
+g
+'
+}