sparse-checkout: update working directory in-process

The sparse-checkout builtin used 'git read-tree -mu HEAD' to update the
skip-worktree bits in the index and to update the working directory.
This extra process is overly complex, and prone to failure. It also
requires that we write our changes to the sparse-checkout file before
trying to update the index.

Remove this extra process call by creating a direct call to
unpack_trees() in the same way 'git read-tree -mu HEAD' does. In
addition, provide an in-memory list of patterns so we can avoid
reading from the sparse-checkout file. This allows us to test a
proposed change to the file before writing to it.

An earlier version of this patch included a bug when the 'set' command
failed due to the "Sparse checkout leaves no entry on working directory"
error. It would not rollback the index.lock file, so the replay of the
old sparse-checkout specification would fail. A test in t1091 now
covers that scenario.

Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 1 insertions, 1 deletions

diff --git a/builtin/read-tree.c b/builtin/read-tree.c
index ca5e655d2f..af7424b94c 100644
--- a/builtin/read-tree.c
+++ b/builtin/read-tree.c
@@ -185,7 +185,7 @@ int cmd_read_tree(int argc, const char **argv, const char *cmd_prefix)
 
 	if (opts.reset || opts.merge || opts.prefix) {
 		if (read_cache_unmerged() && (opts.prefix || opts.merge))
-			die("You need to resolve your current index first");
+			die(_("You need to resolve your current index first"));
 		stage = opts.merge = 1;
 	}
 	resolve_undo_clear();