tests: separate INVASIVE filesystem tests

Introduce GITTEST_INVASIVE_FS_STRUCTURE for things that are invasive
to your filesystem structure (like creating folders at your filesystem
root) and GITTEST_INVASIVE_FS_SIZE for things that write lots of data.

.travis.yml

@@ -15,6 +15,7 @@ compiler:
 env:
  global:
   - secure: "YnhS+8n6B+uoyaYfaJ3Lei7cSJqHDPiKJCKFIF2c87YDfmCvAJke8QtE7IzjYDs7UFkTCM4ox+ph2bERUrxZbSCyEkHdjIZpKuMJfYWja/jgMqTMxdyOH9y8JLFbZsSXDIXDwqBlC6vVyl1fP90M35wuWcNTs6tctfVWVofEFbs="
+  - GITTEST_INVASIVE_FS_SIZE=1
  matrix:
   - OPTIONS="-DTHREADSAFE=ON -DCMAKE_BUILD_TYPE=Release"
   - OPTIONS="-DTHREADSAFE=OFF -DBUILD_EXAMPLES=ON"

appveyor.yml

@@ -3,7 +3,8 @@ branches:
   only:
   - master
 environment:
-  GITTEST_INVASIVE_FILESYSTEM: 1
+  GITTEST_INVASIVE_FS_STRUCTURE: 1
+  GITTEST_INVASIVE_FS_SIZE: 1
 
   matrix:
   - GENERATOR: "Visual Studio 11"

tests/filter/stream.c

@@ -214,7 +214,7 @@ void test_filter_stream__smallfile(void)
 /* optionally write a 500 MB file through the compression stream */
 void test_filter_stream__bigfile(void)
 {
-	if (!cl_getenv("GITTEST_INVASIVE_FILESYSTEM"))
+	if (!cl_getenv("GITTEST_INVASIVE_FS_SIZE"))
 		cl_skip();
 
 	test_stream(51200);

tests/repo/init.c

@@ -722,7 +722,7 @@ void test_repo_init__at_filesystem_root(void)
 	git_buf root = GIT_BUF_INIT;
 	int root_len;
 
-	if (!cl_getenv("GITTEST_INVASIVE_FILESYSTEM"))
+	if (!cl_getenv("GITTEST_INVASIVE_FS_STRUCTURE"))
 		cl_skip();
 
 	root_len = git_path_root(sandbox);