[PATCH 1/1] read-cache: update index format default to v4

From: Derrick Stolee via GitGitGadget <gitgitgadget@gmail.com>
Date: Sep 24, 2018, 21:15 UTC
Message-ID: <56374128136fe9377503d446daf98e67847194aa.1537823728.git.gitgitgadget@gmail.com>
In-Reply-To: <pull.41.git.gitgitgadget@gmail.com>

From: Derrick Stolee <dstolee@microsoft.com>

The index v4 format has been available since 2012 with 9d22778 "reach-cache.c: write prefix-compressed names in the index". Since the format has been stable for so long, almost all versions of Git in use today understand version 4, removing one barrier to upgrade -- that someone may want to downgrade and needs a working repo.

Despite being stable for a long time, this index version was never adopted as the default. This prefix-compressed version of the format can get significant space savings on repos with large working directories (which naturally tend to have deep nesting). This version is set as the default for some external tools, such as VFS for Git. Because of this external use, the format has had a lot of "testing in production" and also is subject to continuous integration in these environments.

Previously, to test version 4 indexes, we needed to run the test suite with GIT_TEST_INDEX_VERSION=4 (or TEST_GIT_INDEX_VERSION=4).

One potential, but short-term, downside is that we lose coverage of the version 3 indexes. The trade-off is that we may want to cover that version using GIT_TEST_INDEX_VERSION=3.

Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
---
 read-cache.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/read-cache.c b/read-cache.c
index 372588260e..af6c8f2a67 100644
--- a/read-cache.c
+++ b/read-cache.c
@@ -1484,7 +1484,7 @@ struct cache_entry *refresh_cache_entry(struct cache_entry *ce,
  * Index File I/O
  *****************************************************************/
 
-#define INDEX_FORMAT_DEFAULT 3
+#define INDEX_FORMAT_DEFAULT 4
 
 static unsigned int get_index_format_default(void)
 {

-- 
gitgitgadget