made the pack completely portable and wrote relevent bat files to go with it

gitportable/mingw64/share/doc/git-doc/date-formats.adoc

@@ -0,0 +1,31 @@
+DATE FORMATS
+------------
+
+The `GIT_AUTHOR_DATE` and `GIT_COMMITTER_DATE` environment variables
+support the following date formats:
+
+Git internal format::
+	It is `<unix-timestamp> <time-zone-offset>`, where
+	`<unix-timestamp>` is the number of seconds since the UNIX epoch.
+	`<time-zone-offset>` is a positive or negative offset from UTC.
+	For example CET (which is 1 hour ahead of UTC) is `+0100`.
+
+RFC 2822::
+	The standard date format as described by RFC 2822, for example
+	`Thu, 07 Apr 2005 22:13:13 +0200`.
+
+ISO 8601::
+	Time and date specified by the ISO 8601 standard, for example
+	`2005-04-07T22:13:13`. The parser accepts a space instead of the
+	`T` character as well. Fractional parts of a second will be ignored,
+	for example `2005-04-07T22:13:13.019` will be treated as
+	`2005-04-07T22:13:13`.
++
+NOTE: In addition, the date part is accepted in the following formats:
+`YYYY.MM.DD`, `MM/DD/YYYY` and `DD.MM.YYYY`.
+
+ifdef::git-commit[]
+In addition to recognizing all date formats above, the `--date` option
+will also try to make sense of other, more human-centric date formats,
+such as relative dates like "yesterday" or "last Friday at noon".
+endif::git-commit[]