Merge core VFS features

These were done in private, before microsoft/git.

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

Documentation/config/core.txt

@@ -743,6 +743,48 @@ core.multiPackIndex::
 	single index. See linkgit:git-multi-pack-index[1] for more
 	information. Defaults to true.
 
+core.gvfs::
+	Enable the features needed for GVFS.  This value can be set to true
+	to indicate all features should be turned on or the bit values listed
+	below can be used to turn on specific features.
++
+--
+	GVFS_SKIP_SHA_ON_INDEX::
+		Bit value 1
+		Disables the calculation of the sha when writing the index
+	GVFS_MISSING_OK::
+		Bit value 4
+		Normally git write-tree ensures that the objects referenced by the
+		directory exist in the object database. This option disables this check.
+	GVFS_NO_DELETE_OUTSIDE_SPARSECHECKOUT::
+		Bit value 8
+		When marking entries to remove from the index and the working
+		directory this option will take into account what the
+		skip-worktree bit was set to so that if the entry has the
+		skip-worktree bit set it will not be removed from the working
+		directory.  This will allow virtualized working directories to
+		detect the change to HEAD and use the new commit tree to show
+		the files that are in the working directory.
+	GVFS_FETCH_SKIP_REACHABILITY_AND_UPLOADPACK::
+		Bit value 16
+		While performing a fetch with a virtual file system we know
+		that there will be missing objects and we don't want to download
+		them just because of the reachability of the commits.  We also
+		don't want to download a pack file with commits, trees, and blobs
+		since these will be downloaded on demand.  This flag will skip the
+		checks on the reachability of objects during a fetch as well as
+		the upload pack so that extraneous objects don't get downloaded.
+	GVFS_BLOCK_FILTERS_AND_EOL_CONVERSIONS::
+		Bit value 64
+		With a virtual file system we only know the file size before any
+		CRLF or smudge/clean filters processing is done on the client.
+		To prevent file corruption due to truncation or expansion with
+		garbage at the end, these filters must not run when the file
+		is first accessed and brought down to the client. Git.exe can't
+		currently tell the first access vs subsequent accesses so this
+		flag just blocks them from occurring at all.
+--
+
 core.sparseCheckout::
 	Enable "sparse checkout" feature. See linkgit:git-sparse-checkout[1]
 	for more information.

Documentation/technical/read-object-protocol.txt

@@ -0,0 +1,102 @@
+Read Object Process
+^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+The read-object process enables Git to read all missing blobs with a
+single process invocation for the entire life of a single Git command.
+This is achieved by using a packet format (pkt-line, see technical/
+protocol-common.txt) based protocol over standard input and standard
+output as follows. All packets, except for the "*CONTENT" packets and
+the "0000" flush packet, are considered text and therefore are
+terminated by a LF.
+
+Git starts the process when it encounters the first missing object that
+needs to be retrieved. After the process is started, Git sends a welcome
+message ("git-read-object-client"), a list of supported protocol version
+numbers, and a flush packet. Git expects to read a welcome response
+message ("git-read-object-server"), exactly one protocol version number
+from the previously sent list, and a flush packet. All further
+communication will be based on the selected version.
+
+The remaining protocol description below documents "version=1". Please
+note that "version=42" in the example below does not exist and is only
+there to illustrate how the protocol would look with more than one
+version.
+
+After the version negotiation Git sends a list of all capabilities that
+it supports and a flush packet. Git expects to read a list of desired
+capabilities, which must be a subset of the supported capabilities list,
+and a flush packet as response:
+------------------------
+packet: git> git-read-object-client
+packet: git> version=1
+packet: git> version=42
+packet: git> 0000
+packet: git< git-read-object-server
+packet: git< version=1
+packet: git< 0000
+packet: git> capability=get
+packet: git> capability=have
+packet: git> capability=put
+packet: git> capability=not-yet-invented
+packet: git> 0000
+packet: git< capability=get
+packet: git< 0000
+------------------------
+The only supported capability in version 1 is "get".
+
+Afterwards Git sends a list of "key=value" pairs terminated with a flush
+packet. The list will contain at least the command (based on the
+supported capabilities) and the sha1 of the object to retrieve. Please
+note, that the process must not send any response before it received the
+final flush packet.
+
+When the process receives the "get" command, it should make the requested
+object available in the git object store and then return success. Git will
+then check the object store again and this time find it and proceed.
+------------------------
+packet: git> command=get
+packet: git> sha1=0a214a649e1b3d5011e14a3dc227753f2bd2be05
+packet: git> 0000
+------------------------
+
+The process is expected to respond with a list of "key=value" pairs
+terminated with a flush packet. If the process does not experience
+problems then the list must contain a "success" status.
+------------------------
+packet: git< status=success
+packet: git< 0000
+------------------------
+
+In case the process cannot or does not want to process the content, it
+is expected to respond with an "error" status.
+------------------------
+packet: git< status=error
+packet: git< 0000
+------------------------
+
+In case the process cannot or does not want to process the content as
+well as any future content for the lifetime of the Git process, then it
+is expected to respond with an "abort" status at any point in the
+protocol.
+------------------------
+packet: git< status=abort
+packet: git< 0000
+------------------------
+
+Git neither stops nor restarts the process in case the "error"/"abort"
+status is set.
+
+If the process dies during the communication or does not adhere to the
+protocol then Git will stop the process and restart it with the next
+object that needs to be processed.
+
+After the read-object process has processed an object it is expected to
+wait for the next "key=value" list containing a command. Git will close
+the command pipe on exit. The process is expected to detect EOF and exit
+gracefully on its own. Git will wait until the process has stopped.
+
+A long running read-object process demo implementation can be found in
+`contrib/long-running-read-object/example.pl` located in the Git core
+repository. If you develop your own long running process then the
+`GIT_TRACE_PACKET` environment variables can be very helpful for
+debugging (see linkgit:git[1]).

GIT-VERSION-GEN

@@ -2,6 +2,9 @@
 
 DEF_VER=v2.48.0-rc0
 
+# Identify microsoft/git via a distinct version suffix
+DEF_VER=$DEF_VER.vfs.0.0
+
 LF='
 '
 
@@ -37,10 +40,15 @@ elif {
 		test -d "${GIT_DIR:-.git}" ||
 		test -f "$SOURCE_DIR"/.git;
 	} &&
-	VN=$(git -C "$SOURCE_DIR" describe --match "v[0-9]*" HEAD 2>/dev/null) &&
+	VN=$(git -C "$SOURCE_DIR" describe --match "v[0-9]*vfs*" HEAD 2>/dev/null) &&
 	case "$VN" in
 	*$LF*) (exit 1) ;;
 	v[0-9]*)
+		if test "${VN%%.vfs.*}" != "${DEF_VER%%.vfs.*}"
+		then
+			echo "Found version $VN, which is not based on $DEF_VER" >&2
+			exit 1
+		fi
 		git -C "$SOURCE_DIR" update-index -q --refresh
 		test -z "$(git -C "$SOURCE_DIR" diff-index --name-only HEAD --)" ||
 		VN="$VN-dirty" ;;

Makefile

@@ -1045,6 +1045,7 @@ LIB_OBJS += git-zlib.o
 LIB_OBJS += gpg-interface.o
 LIB_OBJS += graph.o
 LIB_OBJS += grep.o
+LIB_OBJS += gvfs.o
 LIB_OBJS += hash-lookup.o
 LIB_OBJS += hashmap.o
 LIB_OBJS += help.o

cache-tree.c

@@ -3,6 +3,7 @@
 #include "git-compat-util.h"
 #include "gettext.h"
 #include "hex.h"
+#include "gvfs.h"
 #include "lockfile.h"
 #include "tree.h"
 #include "tree-walk.h"
@@ -260,7 +261,8 @@ static int update_one(struct cache_tree *it,
 		      int flags)
 {
 	struct strbuf buffer;
-	int missing_ok = flags & WRITE_TREE_MISSING_OK;
+	int missing_ok = gvfs_config_is_set(GVFS_MISSING_OK) ?
+		WRITE_TREE_MISSING_OK : (flags & WRITE_TREE_MISSING_OK);
 	int dryrun = flags & WRITE_TREE_DRY_RUN;
 	int repair = flags & WRITE_TREE_REPAIR;
 	int to_invalidate = 0;

commit.c

@@ -1,6 +1,7 @@
 #define USE_THE_REPOSITORY_VARIABLE
 
 #include "git-compat-util.h"
+#include "gvfs.h"
 #include "tag.h"
 #include "commit.h"
 #include "commit-graph.h"
@@ -556,13 +557,17 @@ int repo_parse_commit_internal(struct repository *r,
 		.sizep = &size,
 		.contentp = &buffer,
 	};
+	int ret;
 	/*
 	 * Git does not support partial clones that exclude commits, so set
 	 * OBJECT_INFO_SKIP_FETCH_OBJECT to fail fast when an object is missing.
 	 */
 	int flags = OBJECT_INFO_LOOKUP_REPLACE | OBJECT_INFO_SKIP_FETCH_OBJECT |
-		OBJECT_INFO_DIE_IF_CORRUPT;
-	int ret;
+		    OBJECT_INFO_DIE_IF_CORRUPT;
+
+	/* But the GVFS Protocol _does_ support missing commits! */
+	if (gvfs_config_is_set(GVFS_MISSING_OK))
+		flags ^= OBJECT_INFO_SKIP_FETCH_OBJECT;
 
 	if (!item)
 		return -1;

config.c

@@ -12,6 +12,7 @@
 #include "abspath.h"
 #include "advice.h"
 #include "date.h"
+#include "gvfs.h"
 #include "branch.h"
 #include "config.h"
 #include "parse.h"
@@ -1620,6 +1621,11 @@ int git_default_core_config(const char *var, const char *value,
 		return 0;
 	}
 
+	if (!strcmp(var, "core.gvfs")) {
+		gvfs_load_config_value(value);
+		return 0;
+	}
+
 	if (!strcmp(var, "core.sparsecheckout")) {
 		core_apply_sparse_checkout = git_config_bool(var, value);
 		return 0;
@@ -1650,6 +1656,11 @@ int git_default_core_config(const char *var, const char *value,
 		return 0;
 	}
 
+	if (!strcmp(var, "core.virtualizeobjects")) {
+		core_virtualize_objects = git_config_bool(var, value);
+		return 0;
+	}
+
 	/* Add other config variables here and to Documentation/config.txt. */
 	return platform_core_config(var, value, ctx, cb);
 }

connected.c

@@ -1,8 +1,10 @@
 #define USE_THE_REPOSITORY_VARIABLE
 
 #include "git-compat-util.h"
+#include "environment.h"
 #include "gettext.h"
 #include "hex.h"
+#include "gvfs.h"
 #include "object-store-ll.h"
 #include "run-command.h"
 #include "sigchain.h"
@@ -34,6 +36,26 @@ int check_connected(oid_iterate_fn fn, void *cb_data,
 	struct transport *transport;
 	size_t base_len;
 
+	/*
+	 * Running a virtual file system there will be objects that are
+	 * missing locally and we don't want to download a bunch of
+	 * commits, trees, and blobs just to make sure everything is
+	 * reachable locally so this option will skip reachablility
+	 * checks below that use rev-list.  This will stop the check
+	 * before uploadpack runs to determine if there is anything to
+	 * fetch.  Returning zero for the first check will also prevent the
+	 * uploadpack from happening.  It will also skip the check after
+	 * the fetch is finished to make sure all the objects where
+	 * downloaded in the pack file.  This will allow the fetch to
+	 * run and get all the latest tip commit ids for all the branches
+	 * in the fetch but not pull down commits, trees, or blobs via
+	 * upload pack.
+	 */
+	if (gvfs_config_is_set(GVFS_FETCH_SKIP_REACHABILITY_AND_UPLOADPACK))
+		return 0;
+	if (core_virtualize_objects)
+		return 0;
+
 	if (!opt)
 		opt = &defaults;
 	transport = opt->transport;