[Elijah Newren <newren@palantir.com>]

From: Elijah Newren <newren@gmail.com>

On Thu, Apr 26, 2018 at 5:54 PM, Ben Peart <peartben@gmail.com> wrote:

> Can you write the documentation that clearly explains the exact behavior you
> want?  That would kill two birds with one stone... :)

Sure, something like the following is what I envision, and I've tried to
include the suggestion from Junio to document the copy behavior in the
merge-recursive documentation.

-- 8< --
Subject: [PATCH] fixup! merge: Add merge.renames config setting

---
 Documentation/merge-config.txt     | 3 +--
 Documentation/merge-strategies.txt | 5 +++--
 merge-recursive.c                  | 8 ++++++++
 3 files changed, 12 insertions(+), 4 deletions(-)

diff --git a/Documentation/merge-config.txt b/Documentation/merge-config.txt
index 59848e5634..662c2713ca 100644
--- a/Documentation/merge-config.txt
+++ b/Documentation/merge-config.txt
@@ -41,8 +41,7 @@ merge.renameLimit::
 merge.renames::
 	Whether and how Git detects renames.  If set to "false",
 	rename detection is disabled. If set to "true", basic rename
-	detection is enabled.  If set to "copies" or "copy", Git will
-	detect copies, as well.  Defaults to the value of diff.renames.
+	detection is enabled.  Defaults to the value of diff.renames.
 
 merge.renormalize::
 	Tell Git that canonical representation of files in the
diff --git a/Documentation/merge-strategies.txt b/Documentation/merge-strategies.txt
index 1e0728aa12..aa66cbe41e 100644
--- a/Documentation/merge-strategies.txt
+++ b/Documentation/merge-strategies.txt
@@ -23,8 +23,9 @@ recursive::
 	causing mismerges by tests done on actual merge commits
 	taken from Linux 2.6 kernel development history.
 	Additionally this can detect and handle merges involving
-	renames.  This is the default merge strategy when
-	pulling or merging one branch.
+	renames, but currently cannot make use of detected
+	copies.  This is the default merge strategy when pulling
+	or merging one branch.
 +
 The 'recursive' strategy can take the following options:
 
diff --git a/merge-recursive.c b/merge-recursive.c
index 6cc4404144..b618f134d2 100644
--- a/merge-recursive.c
+++ b/merge-recursive.c
@@ -564,6 +564,14 @@ static struct string_list *get_renames(struct merge_options *o,
 	opts.flags.recursive = 1;
 	opts.flags.rename_empty = 0;
 	opts.detect_rename = merge_detect_rename(o);
+	/*
+	 * We do not have logic to handle the detection of copies.  In
+	 * fact, it may not even make sense to add such logic: would we
+	 * really want a change to a base file to be propagated through
+	 * multiple other files by a merge?
+	 */
+	if (opts.detect_rename > DIFF_DETECT_RENAME)
+		opts.detect_rename = DIFF_DETECT_RENAME;
 	opts.rename_limit = o->merge_rename_limit >= 0 ? o->merge_rename_limit :
 			    o->diff_rename_limit >= 0 ? o->diff_rename_limit :
 			    1000;
-- 
2.17.0.294.g8e3b83c0e3