- add less -I to be able to search case-insensitively

  +17b, but the helptext is quite elaborate, thus:
function                                             old     new   delta
.rodata                                           118995  119032     +37
packed_usage                                       24731   24767     +36
regex_process                                        284     300     +16
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 3/0 up/down: 89/0)               Total: 89 bytes

2 files changed, 6 insertions, 3 deletions

diff --git a/include/usage.h b/include/usage.h
index ac6376afd..24008deeb 100644
--- a/include/usage.h
+++ b/include/usage.h
@@ -2078,7 +2078,7 @@
        "5\n"
 
 #define less_trivial_usage \
-       "[-EMNmh~?] [FILE...]"
+       "[-EMNmh~I?] [FILE...]"
 #define less_full_usage "\n\n" \
        "View a file or list of files. The position within files can be\n" \
        "changed, and files can be manipulated in various ways.\n" \
@@ -2087,6 +2087,7 @@
      "\n        -M,-m   Display a status line containing the line numbers" \
      "\n                and percentage through the file" \
      "\n        -N      Prefix line numbers to each line" \
+     "\n        -I      Ignore case in all searches" \
      "\n        -~      Suppress ~s displayed past the end of the file" \
 
 #define linux32_trivial_usage NOUSAGE_STR
diff --git a/miscutils/less.c b/miscutils/less.c
index 530a40a8c..cd47590ee 100644
--- a/miscutils/less.c
+++ b/miscutils/less.c
@@ -79,6 +79,7 @@ enum {
         FLAG_m = 1 << 2,
         FLAG_N = 1 << 3,
         FLAG_TILDE = 1 << 4,
+        FLAG_I = 1 << 5,
 /* hijack command line options variable for internal state vars */
         LESS_STATE_MATCH_BACKWARDS = 1 << 15,
 };
@@ -965,7 +966,8 @@ static void regex_process(void)
         }
 
         /* Compile the regex and check for errors */
-        err = regcomp_or_errmsg(&pattern, uncomp_regex, 0);
+        err = regcomp_or_errmsg(&pattern, uncomp_regex,
+                                                        option_mask32 & FLAG_I ? REG_ICASE : 0);
         free(uncomp_regex);
         if (err) {
                 print_statusline(err);
@@ -1359,7 +1361,7 @@ int less_main(int argc, char **argv)
         /* TODO: -x: do not interpret backspace, -xx: tab also */
         /* -xxx: newline also */
         /* -w N: assume width N (-xxx -w 32: hex viewer of sorts) */
-        getopt32(argv, "EMmN~");
+        getopt32(argv, "EMmN~I");
         argc -= optind;
         argv += optind;
         num_files = argc;