[PATCH] connected.c: reprepare packs for corner cases

["Derrick Stolee via GitGitGadget" <gitgitgadget@gmail.com>]

From: Derrick Stolee <dstolee@microsoft.com>

While updating the microsoft/git fork on top of v2.26.0-rc0 and
consuming that build into Scalar, I noticed a corner case bug around
partial clone.

The "scalar clone" command can create a Git repository with the
proper config for using partial clone with the "blob:none" filter.
Instead of calling "git clone", it runs "git init" then sets a few
more config values before running "git fetch".

In our builds on v2.26.0-rc0, we noticed that our "git fetch"
command was failing with

  error: https://github.com/microsoft/scalar did not send all necessary objects

This does not happen if you copy the config file from a repository
created by "git clone --filter=blob:none <url>", but it does happen
when adding the config option "core.logAllRefUpdates = true".

By debugging, I was able to see that the loop inside
check_connnected() that checks if all refs are contained in
promisor packs actually did not have any packfiles in the packed_git
list.

I'm not sure what corner-case issues caused this config option to
prevent the reprepare_packed_git() from being called at the proper
spot during the fetch operation. Even worse, I have failed to create
a test case to prevent a regression.

Placing a reprepare_packed_git() call inside chck_connected() before
looping through the packed_git list seems like the safest way to
avoid this issue in the future. While reprepare_packed_git() does
another scan of the pack directory, it is not terribly expensive as
long as we do not run it in a loop. We check connectivity only a
few times per command, so this will not have a meaningful performance
impact. In exchange, we get extra safety around this check.

Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
---
    connected.c: reprepare packs for corner cases
    
    I included how I found this (integrating v2.26.0-rc0 into Scalar), but I
    am able to reproduce it on my Linux machine using real fetches from
    github.com. I'm not sure why I was unable to reproduce the issue in test
    cases using the file:// URLs or the HTTP tests.
    
    Thanks, -Stolee

Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-579%2Fderrickstolee%2Ffetch-reprepare-v1
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-579/derrickstolee/fetch-reprepare-v1
Pull-Request: https://github.com/gitgitgadget/git/pull/579

 connected.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/connected.c b/connected.c
index 7e9bd1bc622..ac52b07b474 100644
--- a/connected.c
+++ b/connected.c
@@ -61,7 +61,11 @@ int check_connected(oid_iterate_fn fn, void *cb_data,
 		 * object is a promisor object. Instead, just make sure we
 		 * received, in a promisor packfile, the objects pointed to by
 		 * each wanted ref.
+		 *
+		 * Before checking for promisor packs, be sure we have the
+		 * latest pack-files loaded into memory.
 		 */
+		reprepare_packed_git(the_repository);
 		do {
 			struct packed_git *p;
 

base-commit: b4374e96c84ed9394fed363973eb540da308ed4f
-- 
gitgitgadget