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[PATCH 2/3] split-index: accept that a base index can be empty

From
Johannes Schindelin via GitGitGadget <gitgitgadget@gmail.com>
Date
Jun 29, 2023, 13:23 UTC
Message-ID
<81118ce106222993ef17586fb0f249d8319f3b90.1688044991.git.gitgitgadget@gmail.com>
In-Reply-To
<pull.1554.git.1688044991.gitgitgadget@gmail.com>
From: Johannes Schindelin <johannes.schindelin@gmx.de>

We are about to fix an ancient bug where `do_read_index()` pretended that the index was not initialized when there are no index entries.

Before the `index_state` structure gained the `initialized` flag in 913e0e99b6a (unpack_trees(): protect the handcrafted in-core index from read_cache(), 2008-08-23), that was the best we could do (even if it was incorrect: it is totally possible to read a Git index file that contains no index entries).

This pattern was repeated also in 998330ac2e7 (read-cache: look for shared index files next to the index, too, 2021-08-26), which we fix here by _not_ mistaking an empty base index for a missing `sharedindex.*` file.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
---
 read-cache.c | 14 ++++++++------
 1 file changed, 8 insertions(+), 6 deletions(-)
diff --git a/read-cache.c b/read-cache.c
index b10caa9831c..e15a472f54f 100644
--- a/read-cache.c
+++ b/read-cache.c
@@ -2455,12 +2455,14 @@ int read_index_from(struct index_state *istate, const char *path,
 
 	base_oid_hex = oid_to_hex(&split_index->base_oid);
 	base_path = xstrfmt("%s/sharedindex.%s", gitdir, base_oid_hex);
-	trace2_region_enter_printf("index", "shared/do_read_index",
-				   the_repository, "%s", base_path);
-	ret = do_read_index(split_index->base, base_path, 0);
-	trace2_region_leave_printf("index", "shared/do_read_index",
-				   the_repository, "%s", base_path);
-	if (!ret) {
+	if (file_exists(base_path)) {
+		trace2_region_enter_printf("index", "shared/do_read_index",
+					the_repository, "%s", base_path);
+
+		ret = do_read_index(split_index->base, base_path, 0);
+		trace2_region_leave_printf("index", "shared/do_read_index",
+					the_repository, "%s", base_path);
+	} else {
 		char *path_copy = xstrdup(path);
 		char *base_path2 = xstrfmt("%s/sharedindex.%s",
 					   dirname(path_copy), base_oid_hex);
-- 
gitgitgadget
Previous: Johannes Schindelin via GitGitGadgetNext: Junio C Hamano
Message 3 of 6 in “commit -a -m: allow the top-level tree to become empty again”
  1. 0/3 commit -a -m: allow the top-level tree to become empty againJohannes Schindelin via GitGitGadget, Jun 29, 2023
  2. 1/3 do_read_index(): always mark index as initialized unless erroring outJohannes Schindelin via GitGitGadget, Jun 29, 2023
  3. 2/3 split-index: accept that a base index can be emptyJohannes Schindelin via GitGitGadget, Jun 29, 2023
  4. Junio C HamanoJun 29, 2023
  5. 3/3 commit -a -m: allow the top-level tree to become empty againJohannes Schindelin via GitGitGadget, Jun 29, 2023
  6. Junio C HamanoJun 29, 2023

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