Subject: [PATCH 2/3] apply.c: do not checkout file when skip-worktree bit set

From: Kevin Willford <[email-masked]>
Date: Fri, 7 Apr 2017 12:23:56 -0700

When using the sparse-checkout feature git should not write to
the working directory for files with the skip-worktree bit on.
With the skip-worktree bit on the file may or may not be in
the working directory and if it is not we don't want or need to
create it by calling checkout_entry.

There are two callers of checkout_target.  Both of which check
that the file does not exist before calling checkout_target.
load_current which make a call to lstat right before calling checkout_target
and check_preimage which will only run checkout_taret it stat_ret
is less than zero.  It sets stat_ret to zero and only if
!stat->cached will it lstat the file and set stat_ret to
something other than zero.

This patch checks if skip-worktree bit is on in checkout_target
and just returns so that the entry doesn't not end up in the
working directory.  This is so that apply will not create a file
in the working directory, then update the index but not keep the
working directory up to date with the changes that happened in the index.

Signed-off-by: Kevin Willford <[email-masked]>
---
 apply.c | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/apply.c b/apply.c
index 0e2caeab9c..0da5d0b7c9 100644
--- a/apply.c
+++ b/apply.c
@@ -3327,6 +3327,24 @@ static int checkout_target(struct index_state *istate,
 {
 	struct checkout costate = CHECKOUT_INIT;
 
+	/*
+	 * Do not checkout the entry if the skipworktree bit is set
+	 *
+	 * Both callers of this method (check_preimage and load_current)
+	 * check for the existance of the file before calling this
+	 * method so we know that the file doesn't exist at this point
+	 * and we don't need to perform that check again here.
+	 * We just need to check the skip-worktree and return.
+	 *
+	 * This is to prevent git from creating a file in the
+	 * working directory that has the skip-worktree bit on,
+	 * then updating the index from the patch and not keeping
+	 * the working directory version up to date with what it
+	 * changed the index version to be.
+	 */
+	if (ce_skip_worktree(ce))
+		return 0;
+
 	costate.refresh_cache = 1;
 	costate.istate = istate;
 	if (checkout_entry(ce, &costate, NULL) || lstat(ce->name, st))
-- 
2.12.2.windows.2.1.g7df5db8d31