Use $marker_length to correctly parse conflict markers

Since Jujutsu v0.25.0, conflict markers are now allowed to be longer
than 7 characters. The new `$marker_length` variable can be used to pass
the length of the markers to the merge tool.

In order to support longer conflict markers, the `merge-args` setting
for jj-diffconflicts needs to be updated to pass the marker length:

    merge-args = [
      "-c", "let g:jj_diffconflicts_marker_length=$marker_length",
      "-c", "JJDiffConflicts!", "$output", "$base", "$left", "$right"
    ]

But unless long conflict markers are used, jj-diffconflicts should still
work without the use of `$marker_length`, or with Jujutsu versions older
than v0.25.0.

References:
- https://jj-vcs.github.io/jj/latest/conflicts/#long-conflict-markers
- https://jj-vcs.github.io/jj/v0.25.0/config/#setting-up-a-custom-merge-tool
- https://github.com/jj-vcs/jj/releases/tag/v0.25.0

Author: rafikdraoui

README.md

@@ -39,7 +39,10 @@ To configure as a merge tool in Jujutsu, add the following to your [Jujutsu conf
 ```toml
 [merge-tools.diffconflicts]
 program = "nvim"
-merge-args = ["-c", "JJDiffConflicts!", "$output", "$base", "$left", "$right"]
+merge-args = [
+    "-c", "let g:jj_diffconflicts_marker_length=$marker_length",
+    "-c", "JJDiffConflicts!", "$output", "$base", "$left", "$right",
+]
 merge-tool-edits-conflict-markers = true
 ```
 
@@ -54,14 +57,17 @@ If you don't want to use the history view, you can instead set `merge-args` to `
 
 ## Test repository
 
-The `make-conflicts.sh` script creates a Jujutsu repository in the `testrepo` directory whose working copy has two conflicted files.
+The `make-conflicts.sh` script creates a Jujutsu repository in the `testrepo` directory whose working copy has conflicted files.
 It can be used to try `jj-diffconflicts` (or any other merge tool).
 
 The first file is `fruits.txt`, which contains the merge conflict described in the [Conflicts][] section of Jujutsu's documentation.
 
 The second file is `poem.txt`, which contains a tricky merge conflict.
 When resolving it, one should keep in mind the points from the [merge tools benchmarks][] to judge its effectiveness.
 
+The third file is `long_markers.txt`, which the contains the merge conflict described in the [Long conflict markers][] section of the Jujutsu's documentation.
+It can be used to test if the merge tool can handle markers of length higher than the default value.
+
 ## Troubleshooting
 
 The plugin includes a health check to detect potential issues that would prevent it from functioning properly.
@@ -97,6 +103,7 @@ _Caveat emptor_
 [diffconflicts]: https://github.com/whiteinge/diffconflicts/
 [jujutsu configuration]: https://jj-vcs.github.io/jj/latest/config/
 [jujutsu]: https://jj-vcs.github.io/jj/
+[long conflict markers]: https://jj-vcs.github.io/jj/latest/conflicts/#long-conflict-markers
 [merge tools benchmarks]: https://github.com/whiteinge/diffconflicts/blob/master/_utils/README.md#mergetool-benchmarks
 [neovim]: https://neovim.io/
 [short video]: https://www.youtube.com/watch?v=Pxgl3Wtf78Y

doc/jj-diffconflicts.txt

@@ -11,9 +11,12 @@ To configure this plugin as a merge tool in Jujutsu, add the following to your
 Jujutsu configuration:
 >
     [merge-tools.diffconflicts]
-    merge-args = ["-c", "JJDiffConflicts!", "$output", "$base", "$left", "$right"]
-    merge-tool-edits-conflict-markers = true
     program = "nvim"
+    merge-args = [
+      "-c", "let g:jj_diffconflicts_marker_length=$marker_length",
+      "-c", "JJDiffConflicts!", "$output", "$base", "$left", "$right",
+    ]
+    merge-tool-edits-conflict-markers = true
 <
 It can then be invoked with `jj resolve --tool diffconflicts`.
 
@@ -33,6 +36,11 @@ Command ~
     files. This requires the `$base`, `$left`, and `$right` files being passed
     as arguments when opening Neovim as a merge tool.
 
+    If a [count] is given, then it is used as the length of the conflict
+    markers. This can be useful when running the command directly instead of
+    invoking it through `jj resolve`. If no [count] is given, then the merge
+    tool will use the default length of 7 to parse conflict markers.
+
     See also: |g:jj_diffconflicts_no_command|
 
 

lua/jj-diffconflicts/init.lua

@@ -18,7 +18,7 @@ local PATTERNS = nil
 -- conflict resolution UI. If the `show_history` argument is true, then it also
 -- includes a history view that displays the two sides of the conflict and
 -- their ancestor.
-M.run = function(show_history)
+M.run = function(show_history, marker_length)
   local ok, jj_version = pcall(M.get_jj_version)
   if not ok then
     vim.notify(
@@ -27,7 +27,14 @@ M.run = function(show_history)
     )
     jj_version = { math.huge, math.huge, math.huge }
   end
-  h.set_patterns(jj_version)
+
+  if marker_length == 0 or marker_length == nil then
+    marker_length = vim.g.jj_diffconflicts_marker_length
+    if marker_length == "" or marker_length == nil then
+      marker_length = 7
+    end
+  end
+  h.set_patterns(jj_version, marker_length)
 
   local ok, raw_conflict = pcall(h.extract_conflict)
   if not ok then
@@ -74,12 +81,12 @@ end
 -- Define regular expression patterns to be used to detect conflict markers. We
 -- cannot just define them as constants, since they can vary based on Jujutsu's
 -- version.
-h.set_patterns = function(jj_version)
+h.set_patterns = function(jj_version, marker_length)
   local marker = {
-    top = "<<<<<<<",
-    bottom = ">>>>>>>",
-    diff = "%%%%%%%",
-    snapshot = "+++++++",
+    top = string.rep("<", marker_length),
+    bottom = string.rep(">", marker_length),
+    diff = string.rep("%", marker_length),
+    snapshot = string.rep("+", marker_length),
   }
 
   if vim.version.lt(jj_version, { 0, 18, 0 }) then

make-conflicts.sh

@@ -30,6 +30,10 @@ apple
 grape
 orange
 EOF
+cat <<EOF >long_markers.txt
+Heading
+=======
+EOF
 ${JJ} bookmark create base
 ${JJ} commit -m 'Initial revision'
 
@@ -50,6 +54,10 @@ apple
 grapefruit
 orange
 EOF
+cat <<EOF >long_markers.txt
+HEADING
+=======
+EOF
 ${JJ} bookmark create left
 ${JJ} describe -m 'Fix syntax mistakes, eat grapefruit'
 
@@ -71,6 +79,10 @@ APPLE
 GRAPE
 ORANGE
 EOF
+cat <<EOF >long_markers.txt
+New Heading
+===========
+EOF
 ${JJ} bookmark create right
 ${JJ} describe -m 'Fix syntax mistakes, ALL CAPS fruits'
 

plugin/jj_diffconflicts.lua

@@ -1,9 +1,11 @@
 if vim.g.jj_diffconflicts_no_command == nil then
   vim.api.nvim_create_user_command("JJDiffConflicts", function(opts)
     local show_history = opts.bang
-    require("jj-diffconflicts").run(show_history)
+    local marker_length = opts.count
+    require("jj-diffconflicts").run(show_history, marker_length)
   end, {
     desc = "Resolve Jujutsu merge conflicts",
-    bang = true,
+    bang = true, -- used to enable "history" view
+    count = true, -- used to supply marker length
   })
 end