[PATCH/RFC] Color merge conflicts

[PATCH/RFC] Color merge conflicts

[Nguyễn Thái Ngọc Duy]

One of the things I notice when watching a normal git user face a
merge conflicts is the output is very verbose (especially when there
are multiple conflicts) and it's hard to spot the important parts to
start resolving conflicts unless you know what to look for.

This is the start to hopefully help that a bit. One thing I'm not sure
is what to color because that affects the config keys we use for
this. If we have to color different things, it's best to go
"color.merge.<slot>" but if this is the only place to color, that slot
thing looks over-engineered.

Perhaps another piece to color is the conflicted path? Maybe. But on
the other hand, I don't think we want a chameleon output, just enough
visual cues to go from one conflict to the next...

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
---
 merge-recursive.c | 133 +++++++++++++++++++++++++++-------------------
 2 files changed, 79 insertions(+), 55 deletions(-)

diff --git a/merge-recursive.c b/merge-recursive.c
index 113c1d6962..b800101538 100644
--- a/merge-recursive.c
+++ b/merge-recursive.c
@@ -26,6 +26,7 @@
 #include "dir.h"
 #include "submodule.h"
 #include "revision.h"
+#include "color.h"
 
 struct path_hashmap_entry {
 	struct hashmap_entry e;
@@ -286,6 +287,28 @@ static void output(struct merge_options *o, int v, const char *fmt, ...)
 		flush_output(o);
 }
 
+__attribute__((format (printf, 3, 4)))
+static void conflict_output(struct merge_options *o, int v, const char *fmt, ...)
+{
+	va_list ap;
+
+	if (!show(o, v))
+		return;
+
+	strbuf_addchars(&o->obuf, ' ', o->call_depth * 2);
+
+	strbuf_addf(&o->obuf, "%s%s%s ",
+		    GIT_COLOR_RED, _("CONFLICT"), GIT_COLOR_RESET);
+
+	va_start(ap, fmt);
+	strbuf_vaddf(&o->obuf, fmt, ap);
+	va_end(ap);
+
+	strbuf_addch(&o->obuf, '\n');
+	if (!o->buffer_output)
+		flush_output(o);
+}
+
 static void output_commit_title(struct merge_options *o, struct commit *commit)
 {
 	struct merge_remote_desc *desc;
@@ -1497,27 +1520,27 @@ static int handle_change_delete(struct merge_options *o,
 		 */
 		if (!alt_path) {
 			if (!old_path) {
-				output(o, 1, _("CONFLICT (%s/delete): %s deleted in %s "
-				       "and %s in %s. Version %s of %s left in tree."),
-				       change, path, delete_branch, change_past,
-				       change_branch, change_branch, path);
+				conflict_output(o, 1, _("(%s/delete): %s deleted in %s "
+							"and %s in %s. Version %s of %s left in tree."),
+						change, path, delete_branch, change_past,
+						change_branch, change_branch, path);
 			} else {
-				output(o, 1, _("CONFLICT (%s/delete): %s deleted in %s "
-				       "and %s to %s in %s. Version %s of %s left in tree."),
-				       change, old_path, delete_branch, change_past, path,
-				       change_branch, change_branch, path);
+				conflict_output(o, 1, _("(%s/delete): %s deleted in %s "
+							"and %s to %s in %s. Version %s of %s left in tree."),
+						change, old_path, delete_branch, change_past, path,
+						change_branch, change_branch, path);
 			}
 		} else {
 			if (!old_path) {
-				output(o, 1, _("CONFLICT (%s/delete): %s deleted in %s "
-				       "and %s in %s. Version %s of %s left in tree at %s."),
-				       change, path, delete_branch, change_past,
-				       change_branch, change_branch, path, alt_path);
+				conflict_output(o, 1, _("(%s/delete): %s deleted in %s "
+							"and %s in %s. Version %s of %s left in tree at %s."),
+						change, path, delete_branch, change_past,
+						change_branch, change_branch, path, alt_path);
 			} else {
-				output(o, 1, _("CONFLICT (%s/delete): %s deleted in %s "
-				       "and %s to %s in %s. Version %s of %s left in tree at %s."),
-				       change, old_path, delete_branch, change_past, path,
-				       change_branch, change_branch, path, alt_path);
+				conflict_output(o, 1, _("(%s/delete): %s deleted in %s "
+							"and %s to %s in %s. Version %s of %s left in tree at %s."),
+						change, old_path, delete_branch, change_past, path,
+						change_branch, change_branch, path, alt_path);
 			}
 		}
 		/*
@@ -1647,12 +1670,12 @@ static int handle_rename_rename_1to2(struct merge_options *o,
 	struct diff_filespec *a = ci->pair1->two;
 	struct diff_filespec *b = ci->pair2->two;
 
-	output(o, 1, _("CONFLICT (rename/rename): "
-	       "Rename \"%s\"->\"%s\" in branch \"%s\" "
-	       "rename \"%s\"->\"%s\" in \"%s\"%s"),
-	       one->path, a->path, ci->branch1,
-	       one->path, b->path, ci->branch2,
-	       o->call_depth ? _(" (left unresolved)") : "");
+	conflict_output(o, 1, _("(rename/rename): "
+				"Rename \"%s\"->\"%s\" in branch \"%s\" "
+				"rename \"%s\"->\"%s\" in \"%s\"%s"),
+			one->path, a->path, ci->branch1,
+			one->path, b->path, ci->branch2,
+			o->call_depth ? _(" (left unresolved)") : "");
 	if (o->call_depth) {
 		struct merge_file_info mfi;
 		struct diff_filespec other;
@@ -1716,11 +1739,11 @@ static int handle_rename_rename_2to1(struct merge_options *o,
 	struct merge_file_info mfi_c2;
 	int ret;
 
-	output(o, 1, _("CONFLICT (rename/rename): "
-	       "Rename %s->%s in %s. "
-	       "Rename %s->%s in %s"),
-	       a->path, c1->path, ci->branch1,
-	       b->path, c2->path, ci->branch2);
+	conflict_output(o, 1, _("(rename/rename): "
+				"Rename %s->%s in %s. "
+				"Rename %s->%s in %s"),
+			a->path, c1->path, ci->branch1,
+			b->path, c2->path, ci->branch2);
 
 	remove_file(o, 1, a->path, o->call_depth || would_lose_untracked(a->path));
 	remove_file(o, 1, b->path, o->call_depth || would_lose_untracked(b->path));
@@ -1973,12 +1996,12 @@ static char *handle_path_level_conflicts(struct merge_options *o,
 		/* This should only happen when entry->non_unique_new_dir set */
 		if (!entry->non_unique_new_dir)
 			BUG("entry->non_unqiue_dir not set and !new_path");
-		output(o, 1, _("CONFLICT (directory rename split): "
-			       "Unclear where to place %s because directory "
-			       "%s was renamed to multiple other directories, "
-			       "with no destination getting a majority of the "
-			       "files."),
-		       path, entry->dir);
+		conflict_output(o, 1, _("(directory rename split): "
+					"Unclear where to place %s because directory "
+					"%s was renamed to multiple other directories, "
+					"with no destination getting a majority of the "
+					"files."),
+				path, entry->dir);
 		clean = 0;
 		return NULL;
 	}
@@ -2005,20 +2028,20 @@ static char *handle_path_level_conflicts(struct merge_options *o,
 		collision_ent->reported_already = 1;
 		strbuf_add_separated_string_list(&collision_paths, ", ",
 						 &collision_ent->source_files);
-		output(o, 1, _("CONFLICT (implicit dir rename): Existing "
-			       "file/dir at %s in the way of implicit "
-			       "directory rename(s) putting the following "
-			       "path(s) there: %s."),
-		       new_path, collision_paths.buf);
+		conflict_output(o, 1, _("(implicit dir rename): Existing "
+					"file/dir at %s in the way of implicit "
+					"directory rename(s) putting the following "
+					"path(s) there: %s."),
+				new_path, collision_paths.buf);
 		clean = 0;
 	} else if (collision_ent->source_files.nr > 1) {
 		collision_ent->reported_already = 1;
 		strbuf_add_separated_string_list(&collision_paths, ", ",
 						 &collision_ent->source_files);
-		output(o, 1, _("CONFLICT (implicit dir rename): Cannot map "
-			       "more than one path to %s; implicit directory "
-			       "renames tried to put these paths there: %s"),
-		       new_path, collision_paths.buf);
+		conflict_output(o, 1, _("(implicit dir rename): Cannot map "
+					"more than one path to %s; implicit directory "
+					"renames tried to put these paths there: %s"),
+				new_path, collision_paths.buf);
 		clean = 0;
 	}
 
@@ -2107,11 +2130,11 @@ static void handle_directory_level_conflicts(struct merge_options *o,
 			 * know that head_ent->new_dir and merge_ent->new_dir
 			 * are different strings.
 			 */
-			output(o, 1, _("CONFLICT (rename/rename): "
-				       "Rename directory %s->%s in %s. "
-				       "Rename directory %s->%s in %s"),
-			       head_ent->dir, head_ent->new_dir.buf, o->branch1,
-			       head_ent->dir, merge_ent->new_dir.buf, o->branch2);
+			conflict_output(o, 1, _("(rename/rename): "
+						"Rename directory %s->%s in %s. "
+						"Rename directory %s->%s in %s"),
+					head_ent->dir, head_ent->new_dir.buf, o->branch1,
+					head_ent->dir, merge_ent->new_dir.buf, o->branch2);
 			string_list_append(&remove_from_head,
 					   head_ent->dir)->util = head_ent;
 			strbuf_release(&head_ent->new_dir);
@@ -2758,10 +2781,10 @@ static int process_renames(struct merge_options *o,
 			} else if (!oid_eq(&dst_other.oid, &null_oid)) {
 				clean_merge = 0;
 				try_merge = 1;
-				output(o, 1, _("CONFLICT (rename/add): Rename %s->%s in %s. "
-				       "%s added in %s"),
-				       ren1_src, ren1_dst, branch1,
-				       ren1_dst, branch2);
+				conflict_output(o, 1, _("(rename/add): Rename %s->%s in %s. "
+							"%s added in %s"),
+						ren1_src, ren1_dst, branch1,
+						ren1_dst, branch2);
 				if (o->call_depth) {
 					struct merge_file_info mfi;
 					if (merge_file_one(o, ren1_dst, &null_oid, 0,
@@ -3079,7 +3102,7 @@ static int merge_content(struct merge_options *o,
 	if (!mfi.clean) {
 		if (S_ISGITLINK(mfi.mode))
 			reason = _("submodule");
-		output(o, 1, _("CONFLICT (%s): Merge conflict in %s"),
+		conflict_output(o, 1, _("(%s): Merge conflict in %s"),
 				reason, path);
 		if (rename_conflict_info && !df_conflict_remains)
 			if (update_stages(o, path, &one, &a, &b))
@@ -3240,9 +3263,9 @@ static int process_entry(struct merge_options *o,
 			       0)) {
 			char *new_path = unique_path(o, path, add_branch);
 			clean_merge = 0;
-			output(o, 1, _("CONFLICT (%s): There is a directory with name %s in %s. "
-			       "Adding %s as %s"),
-			       conf, path, other_branch, path, new_path);
+			conflict_output(o, 1, _("(%s): There is a directory with name %s in %s. "
+						"Adding %s as %s"),
+					conf, path, other_branch, path, new_path);
 			if (update_file(o, 0, oid, mode, new_path))
 				clean_merge = -1;
 			else if (o->call_depth)
-- 
2.18.0.656.gda699b98b3

Re: [PATCH/RFC] Color merge conflicts

[Stefan Beller]

On Mon, Jul 30, 2018 at 9:00 AM Nguyễn Thái Ngọc Duy <pclouds@gmail.com> wrote:
>
> One of the things I notice when watching a normal git user face a
> merge conflicts is the output is very verbose (especially when there
> are multiple conflicts) and it's hard to spot the important parts to
> start resolving conflicts unless you know what to look for.

I usually go by git-status, but I am not the watched normal user,
hopefully. Maybe we want to run git-status after a failed merge
for the user, too, though?

> This is the start to hopefully help that a bit. One thing I'm not sure
> is what to color because that affects the config keys we use for
> this. If we have to color different things, it's best to go
> "color.merge.<slot>" but if this is the only place to color, that slot
> thing looks over-engineered.
>
> Perhaps another piece to color is the conflicted path? Maybe. But on
> the other hand, I don't think we want a chameleon output, just enough
> visual cues to go from one conflict to the next...

I would think we would want to highlight the type of conflict as well,
e.g.

  <RED> CONFLICT> <RESET> \
  <BOLD;RED> (rename/rename): <RESET> \
  Rename a -> b in branch foo \
  rename a ->c in bar

but then again, this patch is better than not doing any colors.

I wonder if we want to have certain colors associated with certain
types of merge conflicts, e.g. anything involving a rename would
be yellow, any conflict with deletion to be dark red, regular merge
conflicts blue (and at the same time we could introduce coloring
of conflict markers to also be blue)
(I am just making up colors, not seriously suggesting them)

I like the idea!

Thanks,
Stefan

Re: [PATCH/RFC] Color merge conflicts

[Elijah Newren]

On Mon, Jul 30, 2018 at 10:40 AM, Stefan Beller <sbeller@google.com> wrote:
> On Mon, Jul 30, 2018 at 9:00 AM Nguyễn Thái Ngọc Duy <pclouds@gmail.com> wrote:
>>
>> One of the things I notice when watching a normal git user face a
>> merge conflicts is the output is very verbose (especially when there
>> are multiple conflicts) and it's hard to spot the important parts to
>> start resolving conflicts unless you know what to look for.
>
> I usually go by git-status, but I am not the watched normal user,
> hopefully. Maybe we want to run git-status after a failed merge
> for the user, too, though?

I'm a little worried the git status output may be long enough that
they miss all the conflict messages and don't even think to scroll
back and look at them.  Since not all conflict types are nicely
representable in git status output, that could be problematic.  (e.g.
renames aren't recorded in the index in any fashion, so git status
can't tell you a conflict was from a rename/delete or
rename/rename(1to2), for example; it's possible that information may
be important in helping the user track down why the working directory
ended up the way it did to help them resolve the conflict.)

If that extra information that is currently only reported in these
conflict messages were recorded somewhere -- either the index or the
working tree -- then it wouldn't be as much of a risk to hide it
behind git status.  In fact, it would seem safer and nicer in general
because users already run the risk of losing those conflict messages.

>> This is the start to hopefully help that a bit. One thing I'm not sure
>> is what to color because that affects the config keys we use for
>> this. If we have to color different things, it's best to go
>> "color.merge.<slot>" but if this is the only place to color, that slot
>> thing looks over-engineered.
>>
>> Perhaps another piece to color is the conflicted path? Maybe. But on
>> the other hand, I don't think we want a chameleon output, just enough
>> visual cues to go from one conflict to the next...
>
> I would think we would want to highlight the type of conflict as well,
> e.g.
>
>   <RED> CONFLICT> <RESET> \
>   <BOLD;RED> (rename/rename): <RESET> \
>   Rename a -> b in branch foo \
>   rename a ->c in bar
>
> but then again, this patch is better than not doing any colors.
>
> I wonder if we want to have certain colors associated with certain
> types of merge conflicts, e.g. anything involving a rename would
> be yellow, any conflict with deletion to be dark red, regular merge
> conflicts blue (and at the same time we could introduce coloring
> of conflict markers to also be blue)

Providing extra hints might be good, but we'd need to flesh out this
idea to avoid edge and corner cases...

What do you do with mixtures, e.g. rename/delete conflicts?  Average
the colors?  Colorize the "rename" differently than the "delete"?

Also, by "regular conflicts" I think you mean the normal content-based
conflict markers we stick in files, rather than path-based conflicts
(like modify/delete or rename/add).  However, something could be both
-- e.g. for an add/add conflict we two-way merge the files so we have
both a path conflict (both sides added a file with that name) and a
content or "regular" conflict (most the files were the same but they
differ on these lines...).  Things could get even crazier with e.g.
rename/add/delete or rename/rename(2to1)/delete.  So, if you want to
colorize regular (or content) conflicts differently than path-based
ones, what do you do when you have both types present?  Does one win?
Do we print multiple conflict messages?  Something else?

> (I am just making up colors, not seriously suggesting them)
>
> I like the idea!
>
> Thanks,
> Stefan