Documentation/line-range-format.txt

<start> and <end> can take one of these forms:

- number
+
If <start> or <end> is a number, it specifies an
absolute line number (lines count from 1).
+

- /regex/
+
This form will use the first line matching the given
POSIX regex. If <start> is a regex, it will search from the end of
the previous `-L` range, if any, otherwise from the start of file.
If <start> is ``^/regex/'', it will search from the start of file.
If <end> is a regex, it will search
starting at the line given by <start>.
+

- +offset or -offset
+
This is only valid for <end> and will specify a number
of lines before or after the line given by <start>.

+
If ``:<regex>'' is given in place of <start> and <end>, it denotes the range
from the first funcname line that matches <regex>, up to the next
funcname line. ``:<regex>'' searches from the end of the previous `-L` range,
if any, otherwise from the start of file.
``^:<regex>'' searches from the start of file.