tq: pass custom transfer adapter args to the shell

When a custom transfer adapter is specified in the configuration, it is
not possible to specify multiple arguments to the process, because only
the last value of the lfs.customtransfer.*.args option is read and the
value is not split.  To make things easier and more flexible,
concatenate the path (after quoting) and the arguments and pass them to
the shell.  Update the documentation to reflect this change.

Update the test custom transfer adapter to parse its arguments (which
are otherwise ignored) and mention them to standard error.  Make the
test check that the arguments are parsed as the shell would expect them
to be.

Author: bk2204

docs/custom-transfers.md

@@ -56,7 +56,8 @@ A custom transfer process is defined under a settings group called
 
   If the custom transfer process requires any arguments, these can be provided
   here. Typically you would only need this if your process was multi-purpose or
-  particularly flexible, most of the time you won't need it.
+  particularly flexible, most of the time you won't need it.  Note that this
+  string will be expanded by the shell.
 
 * `lfs.customtransfer.<name>.concurrent`
 

docs/man/git-lfs-config.5.ronn

@@ -128,7 +128,7 @@ be scoped inside the configuration for a remote.
 * `lfs.customtransfer.<name>.args`
 
   If the custom transfer process requires any arguments, these can be provided
-  here.
+  here.  This string will be expanded by the shell.
 
 * `lfs.customtransfer.<name>.concurrent`
 

t/cmd/lfstest-standalonecustomadapter.go

@@ -28,6 +28,10 @@ func main() {
 		os.Exit(1)
 	}
 
+	for _, arg := range os.Args {
+		writeToStderr(fmt.Sprintf("Saw argument %q\n", arg), errWriter)
+	}
+
 	for scanner.Scan() {
 		line := scanner.Text()
 		var req request

t/t-custom-transfers.sh

@@ -29,7 +29,7 @@ begin_test "custom-transfer-wrong-path"
   # use PIPESTATUS otherwise we get exit code from tee
   res=${PIPESTATUS[0]}
   grep "xfer: adapter \"testcustom\" Begin()" pushcustom.log
-  grep "Failed to start custom transfer command" pushcustom.log
+  grep "xfer: Aborting worker process" pushcustom.log
   if [ "$res" = "0" ]; then
     echo "Push should have failed because of an incorrect custom transfer path."
     exit 1
@@ -123,6 +123,7 @@ begin_test "custom-transfer-standalone"
 
   # set up custom transfer adapter to use a specific transfer agent
   git config lfs.customtransfer.testcustom.path lfstest-standalonecustomadapter
+  git config lfs.customtransfer.testcustom.args "--arg1 '--arg2 --arg3' --arg4"
   git config lfs.customtransfer.testcustom.concurrent false
   git config lfs.standalonetransferagent testcustom
   export TEST_STANDALONE_BACKUP_PATH="$(pwd)/test-custom-transfer-standalone-backup"
@@ -187,6 +188,11 @@ begin_test "custom-transfer-standalone"
 
   grep "Terminating test custom adapter gracefully" fetchcustom.log
 
+  # Test argument parsing.
+  grep 'Saw argument "--arg1"' fetchcustom.log
+  grep 'Saw argument "--arg2 --arg3"' fetchcustom.log
+  grep 'Saw argument "--arg4"' fetchcustom.log
+
   objectlist=`find .git/lfs/objects -type f`
   [ "$(echo "$objectlist" | wc -l)" -eq 12 ]
 )

tq/custom.go

@@ -128,7 +128,8 @@ func (a *customAdapter) WorkerStarting(workerNum int) (interface{}, error) {
 	// Start a process per worker
 	// If concurrent = false we have already dialled back workers to 1
 	a.Trace("xfer: starting up custom transfer process %q for worker %d", a.name, workerNum)
-	cmd := subprocess.ExecCommand(a.path, a.args)
+	cmdName, cmdArgs := subprocess.FormatForShell(subprocess.ShellQuoteSingle(a.path), a.args)
+	cmd := subprocess.ExecCommand(cmdName, cmdArgs...)
 	outp, err := cmd.StdoutPipe()
 	if err != nil {
 		return nil, fmt.Errorf("Failed to get stdout for custom transfer command %q remote: %v", a.path, err)