conflicts: change diff line marker to %%%%%%%

I feel the original -------/+++++++ pair is slightly confusing because
each half can be a separator by itself. I don't know what character other
than '-'/'+' is preferred, but let's pick '%' (for "mod") per @martinvonz
suggestion.

docs/conflicts.md

@@ -87,8 +87,7 @@ how that would look for the same example as above:
 
 ```
 <<<<<<<
--------
-+++++++
+%%%%%%%
  apple
 -grape
 +grapefruit
@@ -101,9 +100,8 @@ ORANGE
 ```
 
 As in Git, the `<<<<<<<` and `>>>>>>>` lines mark the start and end of the
-conflict. The `-------` followed by `+++++++` indicates the start of a diff
-(there is never content between the two header lines). A header consisting of
-only `+++++++` indicates the start of a snapshot (not a diff).
+conflict. The `%%%%%%%` line indicates the start of a diff. The `+++++++`
+line indicates the start of a snapshot (not a diff).
 
 There is another reason for this format (in addition to helping you spot the
 differences): The format supports more complex conflicts involving more than 3

docs/tutorial.md

@@ -234,8 +234,7 @@ There are unresolved conflicts at these paths:
 file1
 $ cat file1
 <<<<<<<
--------
-+++++++
+%%%%%%%
 -b1
 +a
 +++++++

lib/src/conflicts.rs

@@ -25,6 +25,7 @@ use crate::store::Store;
 
 const CONFLICT_START_LINE: &[u8] = b"<<<<<<<\n";
 const CONFLICT_END_LINE: &[u8] = b">>>>>>>\n";
+const CONFLICT_DIFF_LINE: &[u8] = b"%%%%%%%\n";
 const CONFLICT_MINUS_LINE: &[u8] = b"-------\n";
 const CONFLICT_PLUS_LINE: &[u8] = b"+++++++\n";
 
@@ -181,8 +182,7 @@ pub fn materialize_conflict(
                                 .iter()
                                 .position_min_by_key(|diff| diff_size(diff))
                                 .unwrap();
-                            output.write_all(CONFLICT_MINUS_LINE)?;
-                            output.write_all(CONFLICT_PLUS_LINE)?;
+                            output.write_all(CONFLICT_DIFF_LINE)?;
                             write_diff_hunks(&diffs[min_diff_index], output)?;
                             removes.remove(0);
                             adds.remove(min_diff_index);
@@ -278,15 +278,26 @@ pub fn parse_conflict(input: &[u8], num_removes: usize, num_adds: usize) -> Opti
 }
 
 fn parse_conflict_hunk(input: &[u8]) -> MergeHunk {
+    let mut diff_seen = false;
     let mut minus_seen = false;
     let mut plus_seen = false;
     let mut body_seen = false;
     let mut removes = vec![];
     let mut adds = vec![];
     for line in input.split_inclusive(|b| *b == b'\n') {
-        if line == CONFLICT_MINUS_LINE {
+        if line == CONFLICT_DIFF_LINE {
+            diff_seen = true;
+            if body_seen {
+                minus_seen = false;
+                plus_seen = false;
+                body_seen = false;
+            }
+            removes.push(vec![]);
+            adds.push(vec![]);
+        } else if line == CONFLICT_MINUS_LINE {
             minus_seen = true;
             if body_seen {
+                diff_seen = false;
                 plus_seen = false;
                 body_seen = false;
             }
@@ -294,11 +305,12 @@ fn parse_conflict_hunk(input: &[u8]) -> MergeHunk {
         } else if line == CONFLICT_PLUS_LINE {
             plus_seen = true;
             if body_seen {
+                diff_seen = false;
                 minus_seen = false;
                 body_seen = false;
             }
             adds.push(vec![]);
-        } else if minus_seen && plus_seen {
+        } else if diff_seen {
             body_seen = true;
             if let Some(rest) = line.strip_prefix(b"-") {
                 removes.last_mut().unwrap().extend_from_slice(rest);

lib/tests/test_conflicts.rs

@@ -87,8 +87,7 @@ line 5
     line 1
     line 2
     <<<<<<<
-    -------
-    +++++++
+    %%%%%%%
     -line 3
     +right 3.1
     +++++++
@@ -108,8 +107,7 @@ line 5
     line 1
     line 2
     <<<<<<<
-    -------
-    +++++++
+    %%%%%%%
     -line 3
     +right 3.1
     +++++++
@@ -185,8 +183,7 @@ line 5
     line 1
     line 2
     <<<<<<<
-    -------
-    +++++++
+    %%%%%%%
     -line 3
     +++++++
     left
@@ -262,8 +259,7 @@ line 5
     line 1
     line 2
     <<<<<<<
-    -------
-    +++++++
+    %%%%%%%
     -line 3
     +++++++
     right
@@ -297,8 +293,7 @@ fn test_parse_conflict_simple() {
         parse_conflict(
             b"line 1
 <<<<<<<
--------
-+++++++
+%%%%%%%
  line 2
 -line 3
 +left
@@ -328,16 +323,14 @@ fn test_parse_conflict_multi_way() {
         parse_conflict(
             b"line 1
 <<<<<<<
--------
-+++++++
+%%%%%%%
  line 2
 -line 3
 +left
  line 4
 +++++++
 right
--------
-+++++++
+%%%%%%%
  line 2
 +forward
  line 3
@@ -372,8 +365,7 @@ fn test_parse_conflict_different_wrong_arity() {
         parse_conflict(
             b"line 1
 <<<<<<<
--------
-+++++++
+%%%%%%%
  line 2
 -line 3
 +left
@@ -392,8 +384,7 @@ line 5
 
 #[test]
 fn test_parse_conflict_malformed_marker() {
-    // The conflict marker is missing `-------` and `+++++++` (it needs at least one
-    // of them)
+    // The conflict marker is missing `%%%%%%%`
     assert_eq!(
         parse_conflict(
             b"line 1
@@ -421,8 +412,7 @@ fn test_parse_conflict_malformed_diff() {
         parse_conflict(
             b"line 1
 <<<<<<<
--------
-+++++++
+%%%%%%%
  line 2
 -line 3
 +left
@@ -490,7 +480,13 @@ fn test_update_conflict_from_content() {
     assert_eq!(result, None);
 
     // If the conflict is partially resolved, we get a new conflict back.
-    let result = update_conflict_from_content(store, &path, &conflict_id, b"resolved 1\nline 2\n<<<<<<<\n-------\n+++++++\n-line 3\n+left 3\n+++++++\nright 3\n>>>>>>>\n").unwrap();
+    let result = update_conflict_from_content(
+        store,
+        &path,
+        &conflict_id,
+        b"resolved 1\nline 2\n<<<<<<<\n%%%%%%%\n-line 3\n+left 3\n+++++++\nright 3\n>>>>>>>\n",
+    )
+    .unwrap();
     assert_ne!(result, None);
     assert_ne!(result, Some(conflict_id));
     let new_conflict = store.read_conflict(&path, &result.unwrap()).unwrap();

tests/test_interdiff_command.rs

@@ -154,10 +154,9 @@ fn test_interdiff_conflicting() {
     index f845ab93f0...24c5735c3e 100644
     --- a/file
     +++ b/file
-    @@ -1,8 +1,1 @@
+    @@ -1,7 +1,1 @@
     -<<<<<<<
-    --------
-    -+++++++
+    -%%%%%%%
     --foo
     -+abc
     -+++++++

tests/test_obslog_command.rs

@@ -52,10 +52,9 @@ fn test_obslog_with_or_without_diff() {
     | my description
     | Resolved conflict in file1:
     |    1    1: <<<<<<<resolved
-    |    2     : -------
-    |    3     : +++++++
-    |    4     : +bar
-    |    5     : >>>>>>>
+    |    2     : %%%%%%%
+    |    3     : +bar
+    |    4     : >>>>>>>
     o 813918f7b4e6 test.user@example.com 2001-02-03 04:05:08.000 +07:00    conflict
     | my description
     o 8f02f5470c55 test.user@example.com 2001-02-03 04:05:08.000 +07:00   
@@ -91,10 +90,9 @@ fn test_obslog_with_or_without_diff() {
     index e155302a24...2ab19ae607 100644
     --- a/file1
     +++ b/file1
-    @@ -1,5 +1,1 @@
+    @@ -1,4 +1,1 @@
     -<<<<<<<
-    --------
-    -+++++++
+    -%%%%%%%
     -+bar
     ->>>>>>>
     +resolved

tests/test_print_command.rs

@@ -61,8 +61,7 @@ fn test_print() {
     let stdout = test_env.jj_cmd_success(&repo_path, &["print", "file1"]);
     insta::assert_snapshot!(stdout, @r###"
     <<<<<<<
-    -------
-    +++++++
+    %%%%%%%
     -b
     +a
     +++++++

tests/test_touchup_command.rs

@@ -140,8 +140,7 @@ fn test_touchup_merge() {
     let stdout = test_env.jj_cmd_success(&repo_path, &["print", "file2"]);
     insta::assert_snapshot!(stdout, @r###"
     <<<<<<<
-    -------
-    +++++++
+    %%%%%%%
     -a
     +c
     +++++++