in-place option uses different format

[PranavRJoshi]

In GNU sed, the in-place options supports the following format:

$ sed -i script file                              # no backup file produced
$ sed --in-place script file                      # no backup file produced
$ sed -i[SUFFIX] script file                      # backup file of form: file[SUFFIX]
$ sed --in-place=[SUFFIX] script file             # backup file of form: file[SUFFIX]

The current argument parsing function, however, consumes the successive argument for in-place option without checking the form. This is also mentioned in #229.

$ cat temp
quick brown fox

$ ./target/release/sed -i 's/fox/vox/' temp
sed: <script argument 1>:1:1: error: undefined label `emp'

$ sed -i 's/fox/vox/' temp 

$ cat temp
quick brown vox

$ sed -i.bak 's/vox/fox/' temp

$ ls -1
temp
temp.bak

[PranavRJoshi]

For the format:

$ sed -i[SUFFIX] file script

It should be noted that -i and [SUFFIX] must not be space-separated.