Subject: [PATCH v2 3/4] Remove silent clamp of renameLimit

From: Elijah Newren <[email-masked]>
Date: Mon, 13 Nov 2017 12:15:59 -0800

In commit 0024a5492 (Fix the rename detection limit checking; 2007-09-14),
the renameLimit was clamped to 32767.  This appears to have been to simply
avoid integer overflow in the following computation:

   num_create * num_src <= rename_limit * rename_limit

although it also could be viewed as a hardcoded bound on the amount of CPU
time we're willing to allow users to tell git to spend on handling
renames.  An upper bound may make sense, but unfortunately this upper
bound was neither communicated to the users, nor documented anywhere.

Although large limits can make things slow, we have users who would be
ecstatic to have a small five file change be correctly cherry picked even
if they have to manually specify a large limit and wait ten minutes for
the renames to be detected.

Signed-off-by: Elijah Newren <[email-masked]>
---
 diff.c            |  2 +-
 diffcore-rename.c | 11 ++++-------
 2 files changed, 5 insertions(+), 8 deletions(-)

diff --git a/diff.c b/diff.c
index 6fd288420b..c6597e3231 100644
--- a/diff.c
+++ b/diff.c
@@ -5524,7 +5524,7 @@ void diff_warn_rename_limit(const char *varname, int needed, int degraded_cc)
 		warning(_(rename_limit_warning));
 	else
 		return;
-	if (0 < needed && needed < 32767)
+	if (0 < needed)
 		warning(_(rename_limit_advice), varname, needed);
 }
 
diff --git a/diffcore-rename.c b/diffcore-rename.c
index c03f484d53..32366632f4 100644
--- a/diffcore-rename.c
+++ b/diffcore-rename.c
@@ -391,14 +391,10 @@ static int too_many_rename_candidates(int num_create,
 	 * growing larger than a "rename_limit" square matrix, ie:
 	 *
 	 *    num_create * num_src > rename_limit * rename_limit
-	 *
-	 * but handles the potential overflow case specially (and we
-	 * assume at least 32-bit integers)
 	 */
-	if (rename_limit <= 0 || rename_limit > 32767)
-		rename_limit = 32767;
 	if ((num_create <= rename_limit || num_src <= rename_limit) &&
-	    (num_create * num_src <= rename_limit * rename_limit))
+	    ((uint64_t)num_create * (uint64_t)num_src
+	     <= (uint64_t)rename_limit * (uint64_t)rename_limit))
 		return 0;
 
 	options->needed_rename_limit =
@@ -415,7 +411,8 @@ static int too_many_rename_candidates(int num_create,
 		num_src++;
 	}
 	if ((num_create <= rename_limit || num_src <= rename_limit) &&
-	    (num_create * num_src <= rename_limit * rename_limit))
+	    ((uint64_t)num_create * (uint64_t)num_src
+	     <= (uint64_t)rename_limit * (uint64_t)rename_limit))
 		return 2;
 	return 1;
 }
-- 
2.15.0.44.gf995e411c7