Fix field separator issue with no EOF

src/main.rs

@@ -73,7 +73,9 @@ fn main_generic<W: WriteReceiver>(opt: Opt, handle: &mut W) -> Result<()> {
     while let Some(line) = reader.read_line(&mut buffer) {
         match line {
             Ok(l) => {
-                let l = if config.opt.character_wise || config.opt.field_separator.is_some() {
+                let l = if (config.opt.character_wise || config.opt.field_separator.is_some())
+                    && l.ends_with("\n")
+                {
                     &l[0..l.len().saturating_sub(1)]
                 } else {
                     &l

test/choose_colon_1.txt

@@ -0,0 +1,8 @@
+b
+b
+b
+
+efgh
+
+cd
+cd

test/colons.txt

@@ -0,0 +1,8 @@
+a:b
+a:b:c
+a:b:c:d
+
+abcd:efgh
+
+ab:cd:ef:
+ab:cd:

test/e2e_test.sh

@@ -25,6 +25,9 @@ diff -w <(cargo run -- 1:-1 -i ${test_dir}/alphabet.txt 2>/dev/null) <(cat "${te
 diff -w <(cargo run -- 1:-2 -i ${test_dir}/alphabet.txt 2>/dev/null) <(cat "${test_dir}/choose_1x-2.txt")
 diff -w <(cargo run -- 1:-3 -i ${test_dir}/alphabet.txt 2>/dev/null) <(cat "${test_dir}/choose_1x-3.txt")
 # add tests for different delimiters
+diff -w <(cargo run -- -f : 1 -i ${test_dir}/colons.txt 2>/dev/null) <(cat "${test_dir}/choose_colon_1.txt")
+diff -w <(echo a:b | cargo run -- -f : 1) <(echo b)
+diff -w <(echo -n a:b | cargo run -- -f : 1) <(echo b)
 # add tests using piping
 
 set +e