vendor the dependencies

There is a discrepancy of behavior of `github.com/urfave/cli` between
using go1.12 and go1.15, when the dependency is not present as vendored
source. Now this builds fine with go1.12

There are users of tar-split as a package. It is the hope that by adding
this vendored source it does not impact them depending on tar-split
itself.

Signed-off-by: Vincent Batts <vbatts@hashbangbash.com>

vendor/github.com/urfave/cli/funcs.go

@@ -0,0 +1,44 @@
+package cli
+
+// BashCompleteFunc is an action to execute when the bash-completion flag is set
+type BashCompleteFunc func(*Context)
+
+// BeforeFunc is an action to execute before any subcommands are run, but after
+// the context is ready if a non-nil error is returned, no subcommands are run
+type BeforeFunc func(*Context) error
+
+// AfterFunc is an action to execute after any subcommands are run, but after the
+// subcommand has finished it is run even if Action() panics
+type AfterFunc func(*Context) error
+
+// ActionFunc is the action to execute when no subcommands are specified
+type ActionFunc func(*Context) error
+
+// CommandNotFoundFunc is executed if the proper command cannot be found
+type CommandNotFoundFunc func(*Context, string)
+
+// OnUsageErrorFunc is executed if an usage error occurs. This is useful for displaying
+// customized usage error messages.  This function is able to replace the
+// original error messages.  If this function is not set, the "Incorrect usage"
+// is displayed and the execution is interrupted.
+type OnUsageErrorFunc func(context *Context, err error, isSubcommand bool) error
+
+// ExitErrHandlerFunc is executed if provided in order to handle ExitError values
+// returned by Actions and Before/After functions.
+type ExitErrHandlerFunc func(context *Context, err error)
+
+// FlagStringFunc is used by the help generation to display a flag, which is
+// expected to be a single line.
+type FlagStringFunc func(Flag) string
+
+// FlagNamePrefixFunc is used by the default FlagStringFunc to create prefix
+// text for a flag's full name.
+type FlagNamePrefixFunc func(fullName, placeholder string) string
+
+// FlagEnvHintFunc is used by the default FlagStringFunc to annotate flag help
+// with the environment variable details.
+type FlagEnvHintFunc func(envVar, str string) string
+
+// FlagFileHintFunc is used by the default FlagStringFunc to annotate flag help
+// with the file path details.
+type FlagFileHintFunc func(filePath, str string) string