sparse-checkout: use extern for global variables

I noticed this issue when resolving conflicts with our VFS for Git-enabled branch in microsoft/git.

When I moved the global for core.sparseCheckout along with creating the global for core.sparseCheckoutCone, I dropped the "extern" by habit. (We are dropping these from function declarations, usually.) However, this means something different for variables, and could lead to bugs. I haven't found any, but it's better to be safe, right?

Thanks, -Stolee

Derrick Stolee (1):
sparse-checkout: use extern for global variables

 cache.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

base-commit: 99c33bed562b41de6ce9bd3fd561303d39645048
Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-506%2Fderrickstolee%2Fsparse-extern-v1
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-506/derrickstolee/sparse-extern-v1
Pull-Request: https://github.com/gitgitgadget/git/pull/506

gitgitgadget

From: Derrick Stolee <[email protected]>

When the core.sparseCheckoutCone config setting was added in 879321eb0b ("sparse-checkout: add 'cone' mode" 2019-11-21), the variables storing the config values for core.sparseCheckout and core.sparseCheckoutCone were rearranged in cache.h, but in doing so the "extern" keyword was dropped.

While we are tending to drop the "extern" keyword for function declarations, it is still necessary for global variables used across multiple *.c files. The impact of not having the extern keyword may be unpredictable.

---
 cache.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

index 1554488d66..cbfaead23a 100644
@@ -958,8 +958,8 @@ extern int protect_hfs;
 extern int protect_ntfs;
 extern const char *core_fsmonitor;
 
-int core_apply_sparse_checkout;
-int core_sparse_checkout_cone;
+extern int core_apply_sparse_checkout;
+extern int core_sparse_checkout_cone;
 
 /*
  * Include broken refs in all ref iterations, which will

gitgitgadget

"May be unpredictable" might be a bit too strong, but I agree that it is better not to rely on the "common extension" these days, and instead make sure variable decls have "extern" in front.

Will queue. Thanks.