join: implement basic functionality

The basic implementation of join with some tests. The supported
options: -1, -2, -j, -a, -i.

tests/fixtures/join/capitalized.txt

@@ -0,0 +1,4 @@
+A 1
+B 2
+C 4
+D 8

tests/fixtures/join/case_insensitive.expected

@@ -0,0 +1,3 @@
+A 1 2 f
+B 2 3 g
+C 4 4 h

tests/fixtures/join/default.expected

@@ -0,0 +1,5 @@
+1 a
+2 b
+3 c
+5 e
+8 h

tests/fixtures/join/different_field.expected

@@ -0,0 +1,6 @@
+2 b a f
+3 c b g
+4 d c h
+5 e f i
+6 f g j
+7 g h k

tests/fixtures/join/different_fields.expected

@@ -0,0 +1,5 @@
+c 3 2 1 cd
+d 4 3 2 de
+e 5 5 3 ef
+f 6 7 4 fg
+g 7 11 5 gh

tests/fixtures/join/fields_1.txt

@@ -0,0 +1,5 @@
+1
+2
+3
+5
+8

tests/fixtures/join/fields_2.txt

@@ -0,0 +1,9 @@
+1 a
+2 b
+3 c
+4 d
+5 e
+6 f
+7 g
+8 h
+9 i

tests/fixtures/join/fields_3.txt

@@ -0,0 +1,6 @@
+a 2 f
+b 3 g
+c 4 h
+f 5 i
+g 6 j
+h 7 k

tests/fixtures/join/fields_4.txt

@@ -0,0 +1,5 @@
+2 c 1 cd
+3 d 2 de
+5 e 3 ef
+7 f 4 fg
+11 g 5 gh

tests/fixtures/join/unpaired_lines.expected

@@ -0,0 +1,9 @@
+1 a
+2 a f b
+3 b g c
+4 c h d
+5 f i e
+6 g j f
+7 h k g
+8 h
+9 i

tests/test_join.rs

@@ -0,0 +1,95 @@
+use common::util::*;
+
+
+#[test]
+fn empty_files() {
+    new_ucmd!()
+        .arg("empty.txt")
+        .arg("empty.txt")
+        .succeeds().stdout_only("");
+
+    new_ucmd!()
+        .arg("empty.txt")
+        .arg("fields_1.txt")
+        .succeeds().stdout_only("");
+
+    new_ucmd!()
+        .arg("fields_1.txt")
+        .arg("empty.txt")
+        .succeeds().stdout_only("");
+}
+
+#[test]
+fn empty_intersection() {
+    new_ucmd!()
+        .arg("fields_1.txt")
+        .arg("fields_2.txt")
+        .arg("-2")
+        .arg("2")
+        .succeeds().stdout_only("");
+}
+
+#[test]
+fn default_arguments() {
+    new_ucmd!()
+        .arg("fields_1.txt")
+        .arg("fields_2.txt")
+        .succeeds().stdout_only_fixture("default.expected");
+}
+
+#[test]
+fn different_fields() {
+    new_ucmd!()
+        .arg("fields_2.txt")
+        .arg("fields_4.txt")
+        .arg("-j")
+        .arg("2")
+        .succeeds().stdout_only_fixture("different_fields.expected");
+
+    new_ucmd!()
+        .arg("fields_2.txt")
+        .arg("fields_4.txt")
+        .arg("-1")
+        .arg("2")
+        .arg("-2")
+        .arg("2")
+        .succeeds().stdout_only_fixture("different_fields.expected");
+}
+
+#[test]
+fn different_field() {
+    new_ucmd!()
+        .arg("fields_2.txt")
+        .arg("fields_3.txt")
+        .arg("-2")
+        .arg("2")
+        .succeeds().stdout_only_fixture("different_field.expected");
+}
+
+#[test]
+fn unpaired_lines() {
+    new_ucmd!()
+        .arg("fields_2.txt")
+        .arg("fields_3.txt")
+        .arg("-a")
+        .arg("1")
+        .succeeds().stdout_only_fixture("fields_2.txt");
+
+    new_ucmd!()
+        .arg("fields_3.txt")
+        .arg("fields_2.txt")
+        .arg("-1")
+        .arg("2")
+        .arg("-a")
+        .arg("2")
+        .succeeds().stdout_only_fixture("unpaired_lines.expected");
+}
+
+#[test]
+fn case_insensitive() {
+    new_ucmd!()
+        .arg("capitalized.txt")
+        .arg("fields_3.txt")
+        .arg("-i")
+        .succeeds().stdout_only_fixture("case_insensitive.expected");
+}

tests/tests.rs

@@ -58,6 +58,7 @@ generic! {
     "fold", test_fold;
     "hashsum", test_hashsum;
     "head", test_head;
+    "join", test_join;
     "link", test_link;
     "ln", test_ln;
     "ls", test_ls;