gvfs-helper: create tool to fetch objects using the GVFS Protocol

Create gvfs-helper.  This is a helper tool to use the GVFS Protocol
REST API to fetch objects and configuration data from a GVFS cache-server
or Git server.  This tool uses libcurl to send object requests to either
server.  This tool creates loose objects and/or packfiles.

Create gvfs-helper-client.  This code resides within git proper and
uses the sub-process API to manage gvfs-helper as a long-running background
process.

Signed-off-by: Jeff Hostetler <jeffhost@microsoft.com>
Signed-off-by: Derrick Stolee <dstolee@microsoft.com>

Author: jeffhostetler

.gitignore

@@ -77,6 +77,7 @@
 /git-gc
 /git-get-tar-commit-id
 /git-grep
+/git-gvfs-helper
 /git-hash-object
 /git-help
 /git-hook

Documentation/config.txt

@@ -437,6 +437,8 @@ include::config/gui.txt[]
 
 include::config/guitool.txt[]
 
+include::config/gvfs.txt[]
+
 include::config/help.txt[]
 
 include::config/http.txt[]

Documentation/config/core.txt

@@ -778,6 +778,9 @@ core.gvfs::
 		flag just blocks them from occurring at all.
 --
 
+core.useGvfsHelper::
+	TODO
+
 core.sparseCheckout::
 	Enable "sparse checkout" feature. See linkgit:git-sparse-checkout[1]
 	for more information.

Documentation/config/gvfs.txt

@@ -0,0 +1,5 @@
+gvfs.cache-server::
+	TODO
+
+gvfs.sharedcache::
+	TODO

Makefile

@@ -969,6 +969,7 @@ LIB_OBJS += gpg-interface.o
 LIB_OBJS += graph.o
 LIB_OBJS += grep.o
 LIB_OBJS += gvfs.o
+LIB_OBJS += gvfs-helper-client.o
 LIB_OBJS += hash-lookup.o
 LIB_OBJS += hashmap.o
 LIB_OBJS += help.o
@@ -1502,6 +1503,8 @@ else
 	endif
 	BASIC_CFLAGS += $(CURL_CFLAGS)
 
+	PROGRAM_OBJS += gvfs-helper.o
+
 	REMOTE_CURL_PRIMARY = git-remote-http$X
 	REMOTE_CURL_ALIASES = git-remote-https$X git-remote-ftp$X git-remote-ftps$X
 	REMOTE_CURL_NAMES = $(REMOTE_CURL_PRIMARY) $(REMOTE_CURL_ALIASES)
@@ -2734,6 +2737,10 @@ contrib/scalar/scalar$X: $(SCALAR_OBJECTS) GIT-LDFLAGS $(GITLIBS)
 	$(QUIET_LINK)$(CC) $(ALL_CFLAGS) -o $@ $(ALL_LDFLAGS) \
 		$(filter %.o,$^) $(LIBS)
 
+git-gvfs-helper$X: gvfs-helper.o http.o GIT-LDFLAGS $(GITLIBS)
+	$(QUIET_LINK)$(CC) $(ALL_CFLAGS) -o $@ $(ALL_LDFLAGS) $(filter %.o,$^) \
+		$(CURL_LIBCURL) $(EXPAT_LIBEXPAT) $(LIBS)
+
 $(LIB_FILE): $(LIB_OBJS)
 	$(QUIET_AR)$(RM) $@ && $(AR) $(ARFLAGS) $@ $^
 

cache.h

@@ -1079,6 +1079,9 @@ extern int core_gvfs;
 extern int precomposed_unicode;
 extern int protect_hfs;
 extern int protect_ntfs;
+extern int core_use_gvfs_helper;
+extern const char *gvfs_cache_server_url;
+extern const char *gvfs_shared_cache_pathname;
 
 extern int core_apply_sparse_checkout;
 extern int core_sparse_checkout_cone;

config.c

@@ -24,6 +24,7 @@
 #include "color.h"
 #include "refs.h"
 #include "worktree.h"
+#include "transport.h"
 
 struct config_source {
 	struct config_source *prev;
@@ -1735,6 +1736,11 @@ int git_default_core_config(const char *var, const char *value, void *cb)
 		return 0;
 	}
 
+	if (!strcmp(var, "core.usegvfshelper")) {
+		core_use_gvfs_helper = git_config_bool(var, value);
+		return 0;
+	}
+
 	if (!strcmp(var, "core.sparsecheckout")) {
 		/* virtual file system relies on the sparse checkout logic so force it on */
 		if (core_virtualfilesystem)
@@ -1877,6 +1883,37 @@ static int git_default_mailmap_config(const char *var, const char *value)
 	return 0;
 }
 
+static int git_default_gvfs_config(const char *var, const char *value)
+{
+	if (!strcmp(var, "gvfs.cache-server")) {
+		const char *v2 = NULL;
+
+		if (!git_config_string(&v2, var, value) && v2 && *v2)
+			gvfs_cache_server_url = transport_anonymize_url(v2);
+		free((char*)v2);
+		return 0;
+	}
+
+	if (!strcmp(var, "gvfs.sharedcache") && value && *value) {
+		struct strbuf buf = STRBUF_INIT;
+		strbuf_addstr(&buf, value);
+		if (strbuf_normalize_path(&buf) < 0) {
+			/*
+			 * Pretend it wasn't set.  This will cause us to
+			 * fallback to ".git/objects" effectively.
+			 */
+			strbuf_release(&buf);
+			return 0;
+		}
+		strbuf_trim_trailing_dir_sep(&buf);
+
+		gvfs_shared_cache_pathname = strbuf_detach(&buf, NULL);
+		return 0;
+	}
+
+	return 0;
+}
+
 int git_default_config(const char *var, const char *value, void *cb)
 {
 	if (starts_with(var, "core."))
@@ -1926,6 +1963,9 @@ int git_default_config(const char *var, const char *value, void *cb)
 	if (starts_with(var, "sparse."))
 		return git_default_sparse_config(var, value);
 
+	if (starts_with(var, "gvfs."))
+		return git_default_gvfs_config(var, value);
+
 	/* Add other config variables here and to Documentation/config.txt. */
 	return 0;
 }

contrib/buildsystems/CMakeLists.txt

@@ -643,7 +643,7 @@ if(NOT CURL_FOUND)
 	add_compile_definitions(NO_CURL)
 	message(WARNING "git-http-push and git-http-fetch will not be built")
 else()
-	list(APPEND PROGRAMS_BUILT git-http-fetch git-http-push git-imap-send git-remote-http)
+	list(APPEND PROGRAMS_BUILT git-http-fetch git-http-push git-imap-send git-remote-http git-gvfs-helper)
 	if(CURL_VERSION_STRING VERSION_GREATER_EQUAL 7.34.0)
 		add_compile_definitions(USE_CURL_FOR_IMAP_SEND)
 	endif()
@@ -808,6 +808,9 @@ if(CURL_FOUND)
 		add_executable(git-http-push ${CMAKE_SOURCE_DIR}/http-push.c)
 		target_link_libraries(git-http-push http_obj common-main ${CURL_LIBRARIES} ${EXPAT_LIBRARIES})
 	endif()
+
+	add_executable(git-gvfs-helper ${CMAKE_SOURCE_DIR}/gvfs-helper.c)
+	target_link_libraries(git-gvfs-helper http_obj common-main ${CURL_LIBRARIES} )
 endif()
 
 parse_makefile_for_executables(git_builtin_extra "BUILT_INS")

environment.c

@@ -89,6 +89,9 @@ int protect_hfs = PROTECT_HFS_DEFAULT;
 #define PROTECT_NTFS_DEFAULT 1
 #endif
 int protect_ntfs = PROTECT_NTFS_DEFAULT;
+int core_use_gvfs_helper;
+const char *gvfs_cache_server_url;
+const char *gvfs_shared_cache_pathname;
 
 /*
  * The character that begins a commented line in user-editable file