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.adoc

@@ -449,6 +449,8 @@ include::config/gui.adoc[]
 
 include::config/guitool.adoc[]
 
+include::config/gvfs.adoc[]
+
 include::config/help.adoc[]
 
 include::config/http.adoc[]

Documentation/config/core.adoc

@@ -812,6 +812,9 @@ 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.adoc

@@ -0,0 +1,7 @@
+gvfs.cache-server::
+	When set, redirect all GVFS Protocol requests to this base URL instead
+	of the origin server.
+
+gvfs.sharedcache::
+	When set, place all object data downloaded via the GVFS Protocol into
+	this Git alternate.

Documentation/lint-manpages.sh

@@ -27,6 +27,7 @@ check_missing_docs () (
 		git-init-db) continue;;
 		git-remote-*) continue;;
 		git-stage) continue;;
+		git-gvfs-helper) continue;;
 		git-legacy-*) continue;;
 		git-?*--?* ) continue ;;
 		esac

Makefile

@@ -1173,6 +1173,7 @@ 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 += hash.o
 LIB_OBJS += hashmap.o
@@ -1810,6 +1811,8 @@ endif
         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) $(REMOTE_CURL_ALIASES)
@@ -3070,6 +3073,10 @@ scalar$X: scalar.o 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) $(LAZYLOAD_LIBCURL_OBJ)
+	$(QUIET_LINK)$(CC) $(ALL_CFLAGS) -o $@ $(ALL_LDFLAGS) $(filter %.o,$^) \
+		$(CURL_LIBCURL) $(EXPAT_LIBEXPAT) $(LIBS)
+
 $(LIB_FILE): $(LIB_OBJS)
 	$(QUIET_AR)$(RM) $@ && $(AR) $(ARFLAGS) $@ $^
 

config.c

@@ -37,6 +37,7 @@
 #include "trace2.h"
 #include "wildmatch.h"
 #include "write-or-die.h"
+#include "transport.h"
 
 struct config_source {
 	struct config_source *prev;

contrib/buildsystems/CMakeLists.txt

@@ -638,7 +638,7 @@ 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()
@@ -814,6 +814,9 @@ 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

@@ -34,6 +34,7 @@
 #include "quote.h"
 #include "chdir-notify.h"
 #include "setup.h"
+#include "transport.h"
 #include "ws.h"
 #include "write-or-die.h"
 
@@ -92,6 +93,9 @@ int protect_hfs = PROTECT_HFS_DEFAULT;
 #define PROTECT_NTFS_DEFAULT 1
 #endif
 int protect_ntfs = PROTECT_NTFS_DEFAULT;
+int core_use_gvfs_helper;
+char *gvfs_cache_server_url;
+const char *gvfs_shared_cache_pathname;
 
 /*
  * The character that begins a commented line in user-editable file
@@ -522,6 +526,11 @@ int git_default_core_config(const char *var, const char *value,
 		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)
@@ -663,6 +672,39 @@ 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")) {
+		char *v2 = NULL;
+
+		if (!git_config_string(&v2, var, value) && v2 && *v2) {
+			free(gvfs_cache_server_url);
+			gvfs_cache_server_url = transport_anonymize_url(v2);
+		}
+		free(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;
+}
+
 static int git_default_attr_config(const char *var, const char *value)
 {
 	if (!strcmp(var, "attr.tree")) {
@@ -730,6 +772,9 @@ int git_default_config(const char *var, const char *value,
 	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.adoc. */
 	return 0;
 }

environment.h

@@ -163,6 +163,9 @@ extern char *core_virtualfilesystem;
 extern int precomposed_unicode;
 extern int protect_hfs;
 extern int protect_ntfs;
+extern int core_use_gvfs_helper;
+extern char *gvfs_cache_server_url;
+extern const char *gvfs_shared_cache_pathname;
 
 extern int core_apply_sparse_checkout;
 extern int core_sparse_checkout_cone;