[PATCH 1/3] Add support for new %w wildcard in checkout filter

[Calum McConnell <calumlikesapplepie@gmail.com>]

When building content filters with gitattributes, for instance to ensure
git stores the plain-text rather than the binary form of data for certain
formats, it is often advantageous to separate the filters into separate,
potentially complex scripts.  However, as the $PWD where content filters
are executed is unspecified the path to scripts needs to be specified as
an absolute path.  That means that the guide for setting up a repository
which uses scripts to filter content cannot simply consist of "include
the following lines in your .git/config file", and it means that the
otherwise safe operation of moving a git repository from one folder to
another is decidedly unsafe.

This %w (short for 'work tree') will allow such scripts to exist and
be executed on each checkout, without needing to be added to the PATH
or be dependent upon the $PWD of the checkout call.

Signed-off-by: Calum McConnell <calumlikesapplepie@gmail.com>
---
 convert.c | 20 ++++++++++++++------
 1 file changed, 14 insertions(+), 6 deletions(-)

diff --git a/convert.c b/convert.c
index 0d6fb3410a..5d64ccce57 100644
--- a/convert.c
+++ b/convert.c
@@ -9,6 +9,7 @@
 #include "sub-process.h"
 #include "utf8.h"
 #include "ll-merge.h"
+#include "repository.h"
 
 /*
  * convert.c - convert a file when checking it out and checking it in.
@@ -630,19 +631,26 @@ static int filter_buffer_or_fd(int in, int out, void *data)
 
 	/* apply % substitution to cmd */
 	struct strbuf cmd = STRBUF_INIT;
-	struct strbuf path = STRBUF_INIT;
+	struct strbuf filePath = STRBUF_INIT;
+	struct strbuf worktreePath = STRBUF_INIT;
 	struct strbuf_expand_dict_entry dict[] = {
 		{ "f", NULL, },
+		{ "w", NULL, }, 
 		{ NULL, NULL, },
 	};
 
-	/* quote the path to preserve spaces, etc. */
-	sq_quote_buf(&path, params->path);
-	dict[0].value = path.buf;
+	/* quote the paths to preserve spaces, etc. */
+	sq_quote_buf(&filePath, params->path);
+	dict[0].value = filePath.buf;
+	
+	sq_quote_buf(&worktreePath, the_repository->worktree);
+	dict[1].value = worktreePath.buf;
 
-	/* expand all %f with the quoted path */
+	/* expand all %f or %w with the quoted path */
 	strbuf_expand(&cmd, params->cmd, strbuf_expand_dict_cb, &dict);
-	strbuf_release(&path);
+	strbuf_release(&filePath);
+  	strbuf_release(&worktreePath);
+
 
 	strvec_push(&child_process.args, cmd.buf);
 	child_process.use_shell = 1;
-- 
2.30.2