From 4738d90516c8ae83aab844a76cd4b2468caad2b4 Mon Sep 17 00:00:00 2001
From: Ori Bernstein <ori@eigenstate.org>
Date: Sun, 21 Jan 2024 03:07:25 +0000
Subject: [PATCH] diff(1): docuemnt merge3

---
 sys/man/1/diff            | 43 ++++++++++++++++++++++++++++++++++++++-
 sys/src/cmd/diff/merge3.c |  2 +-
 2 files changed, 43 insertions(+), 2 deletions(-)

diff --git a/sys/man/1/diff b/sys/man/1/diff
index 771ccc83f..e0f89c980 100644
--- a/sys/man/1/diff
+++ b/sys/man/1/diff
@@ -5,8 +5,11 @@ diff \- differential file comparator
 .B diff
 [
 .B -abcefmnruw
-] 
+]
 .I file1 ... file2
+.PP
+.B merge3
+.I left common right
 .SH DESCRIPTION
 .I Diff
 tells what lines must be changed in two files to bring them
@@ -165,6 +168,44 @@ Except in rare circumstances,
 .I diff
 finds a smallest sufficient set of file
 differences.
+.PP
+Merge3 merges the contents of
+.I left
+and
+.I right
+using
+.I common
+as a common reference between the two files.
+Changes between
+.IR left ,
+.I right
+and
+.I common
+are computed.
+Any change which does not conflict is output directly.
+When a change does conflict, that is to say,
+affects the same lines of the output file,
+then the change is output with conflict markers.
+The conflict markers look like this:
+.IP
+.EX
+leading content
+<<<<<<<<<< leftfile
+this is an edit made
+to the left file
+========== original
+this is the initial content
+========== rightfile
+here is something that was
+written into the right file
+>>>>>>>>>>
+trailing content
+.EE
+.PP
+If no conflicts are detected,
+.I merge3
+exits with a nil status,
+otherwise it exits with a status of "conflicted".
 .SH FILES
 .B /tmp/diff[12]
 .SH SOURCE
diff --git a/sys/src/cmd/diff/merge3.c b/sys/src/cmd/diff/merge3.c
index 2dd6755e3..26397f3fe 100644
--- a/sys/src/cmd/diff/merge3.c
+++ b/sys/src/cmd/diff/merge3.c
@@ -155,11 +155,11 @@ merge(Diff *l, Diff *r)
 				Bprint(&stdout, "========== %s\n", r->file2);
 				fetch(r, r->ixnew, rc->newx, rc->newy, r->input[1], "");
 				Bprint(&stdout, ">>>>>>>>>>\n");
+				status = "conflict";
 			}
 			ln = y+1;
 			il++;
 			ir++;
-			status = "conflict";
 		}else if(rc == nil || (lc != nil && lx < rx)){
 			fetch(l, l->ixold, ln, lc->oldx-1, l->input[0], "");
 			fetch(l, l->ixnew, lc->newx, lc->newy, l->input[1], "");