Merge branch 'sr/gfi-options'

* sr/gfi-options:
  fast-import: add (non-)relative-marks feature
  fast-import: allow for multiple --import-marks= arguments
  fast-import: test the new option command
  fast-import: add option command
  fast-import: add feature command
  fast-import: put marks reading in its own function
  fast-import: put option parsing code in separate functions

Author: gitster

Documentation/git-fast-import.txt

@@ -75,6 +75,20 @@ OPTIONS
 	set of marks.  If a mark is defined to different values,
 	the last file wins.
 
+--relative-marks::
+	After specifying --relative-marks= the paths specified
+	with --import-marks= and --export-marks= are relative
+	to an internal directory in the current repository.
+	In git-fast-import this means that the paths are relative
+	to the .git/info/fast-import directory. However, other
+	importers may use a different location.
+
+--no-relative-marks::
+	Negates a previous --relative-marks. Allows for combining
+	relative and non-relative marks by interweaving
+	--(no-)-relative-marks= with the --(import|export)-marks=
+	options.
+
 --export-pack-edges=<file>::
 	After creating a packfile, print a line of data to
 	<file> listing the filename of the packfile and the last
@@ -303,6 +317,15 @@ and control the current import process.  More detailed discussion
 	standard output.  This command is optional and is not needed
 	to perform an import.
 
+`feature`::
+	Require that fast-import supports the specified feature, or
+	abort if it does not.
+
+`option`::
+	Specify any of the options listed under OPTIONS that do not
+	change stream semantic to suit the frontend's needs. This
+	command is optional and is not needed to perform an import.
+
 `commit`
 ~~~~~~~~
 Create or update a branch with a new commit, recording one logical
@@ -846,6 +869,62 @@ Placing a `progress` command immediately after a `checkpoint` will
 inform the reader when the `checkpoint` has been completed and it
 can safely access the refs that fast-import updated.
 
+`feature`
+~~~~~~~~~
+Require that fast-import supports the specified feature, or abort if
+it does not.
+
+....
+	'feature' SP <feature> LF
+....
+
+The <feature> part of the command may be any string matching
+^[a-zA-Z][a-zA-Z-]*$ and should be understood by fast-import.
+
+Feature work identical as their option counterparts with the
+exception of the import-marks feature, see below.
+
+The following features are currently supported:
+
+* date-format
+* import-marks
+* export-marks
+* relative-marks
+* no-relative-marks
+* force
+
+The import-marks behaves differently from when it is specified as
+commandline option in that only one "feature import-marks" is allowed
+per stream. Also, any --import-marks= specified on the commandline
+will override those from the stream (if any).
+
+`option`
+~~~~~~~~
+Processes the specified option so that git fast-import behaves in a
+way that suits the frontend's needs.
+Note that options specified by the frontend are overridden by any
+options the user may specify to git fast-import itself.
+
+....
+    'option' SP <option> LF
+....
+
+The `<option>` part of the command may contain any of the options
+listed in the OPTIONS section that do not change import semantics,
+without the leading '--' and is treated in the same way.
+
+Option commands must be the first commands on the input (not counting
+feature commands), to give an option command after any non-option
+command is an error.
+
+The following commandline options change import semantics and may therefore
+not be passed as option:
+
+* date-format
+* import-marks
+* export-marks
+* force
+
 Crash Reports
 -------------
 If fast-import is supplied invalid input it will terminate with a