Synonyms: -i == --regexp-ignore-case, -E == --extended-regexp

These options to log family were too long to type.  Give them
shorter synonyms.

Fix the parsing of the long options while at it.

Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/git-rev-list.txt

@@ -27,7 +27,8 @@ SYNOPSIS
 	     [ \--cherry-pick ]
 	     [ \--encoding[=<encoding>] ]
 	     [ \--(author|committer|grep)=<pattern> ]
-	     [ \--regexp-ignore-case ] [ \--extended-regexp ]
+	     [ \--regexp-ignore-case | \-i ]
+	     [ \--extended-regexp | \-E ]
 	     [ \--date={local|relative|default|iso|rfc|short} ]
 	     [ [\--objects | \--objects-edge] [ \--unpacked ] ]
 	     [ \--pretty | \--header ]
@@ -227,11 +228,11 @@ limiting may be applied.
 	Limit the commits output to ones with log message that
 	matches the specified pattern (regular expression).
 
---regexp-ignore-case::
+-i, --regexp-ignore-case::
 
 	Match the regexp limiting patterns without regard to letters case.
 
---extended-regexp::
+-E, --extended-regexp::
 
 	Consider the limiting patterns to be extended regular expressions
 	instead of the default basic regular expressions.

revision.c

@@ -1165,11 +1165,13 @@ int setup_revisions(int argc, const char **argv, struct rev_info *revs, const ch
 				add_message_grep(revs, arg+7);
 				continue;
 			}
-			if (!prefixcmp(arg, "--extended-regexp")) {
+			if (!strcmp(arg, "--extended-regexp") ||
+			    !strcmp(arg, "-E")) {
 				regflags |= REG_EXTENDED;
 				continue;
 			}
-			if (!prefixcmp(arg, "--regexp-ignore-case")) {
+			if (!strcmp(arg, "--regexp-ignore-case") ||
+			    !strcmp(arg, "-i")) {
 				regflags |= REG_ICASE;
 				continue;
 			}