flux-filemap: use optparse_get_size_int() for size options

Problem: The flux-filemap(1) --chunksize and --small-file-threshold
options take arguments in bytes, but do not support common suffixes
like k, K, M, or G. This makes the options more cumbersome to use
than necessary.

Use optparse_get_size_int() to fetch the value of these options,
which allows the argument to be specified as a floating point number
with optional suffix in the set [kKMG] (up to but not including 2G).

Author: grondo

src/cmd/builtin/filemap.c

@@ -29,8 +29,8 @@
 #include "src/common/libfilemap/filemap.h"
 #include "src/common/libutil/fileref.h"
 
-static const int default_chunksize = 1048576;
-static const int default_small_file_threshold = 4096;
+static const char *default_chunksize = "1M";
+static const char *default_small_file_threshold = "4K";
 
 static json_t *get_list_option (optparse_t *p,
                                 const char *name,
@@ -175,10 +175,12 @@ static int subcmd_map (optparse_t *p, int ac, char *av[])
     }
     ctx.p = p;
     ctx.verbose = optparse_get_int (p, "verbose", 0);
-    ctx.chunksize = optparse_get_int (p, "chunksize", default_chunksize);
-    ctx.threshold = optparse_get_int (p,
-                                      "small-file-threshold",
-                                      default_small_file_threshold);
+    ctx.chunksize = optparse_get_size_int (p,
+                                           "chunksize",
+                                           default_chunksize);
+    ctx.threshold = optparse_get_size_int (p,
+                                           "small-file-threshold",
+                                           default_small_file_threshold);
     ctx.disable_mmap = optparse_hasopt (p, "disable-mmap");
     ctx.tags = get_list_option (p, "tags", "main");
     ctx.h = builtin_get_flux_handle (p);
@@ -375,12 +377,12 @@ static struct optparse_option map_opts[] = {
       .usage = "Change to DIR before mapping", },
     { .name = "verbose", .key = 'v', .has_arg = 2, .arginfo = "[LEVEL]",
       .usage = "Increase output detail.", },
-    { .name = "chunksize", .has_arg = 1, .arginfo = "N",
+    { .name = "chunksize", .has_arg = 1, .arginfo = "N[KMG]",
       .usage = "Limit blob size to N bytes with 0=unlimited"
-               " (default 1048576)", },
-    { .name = "small-file-threshold", .has_arg = 1, .arginfo = "N",
+               " (default 1M)", },
+    { .name = "small-file-threshold", .has_arg = 1, .arginfo = "N[KMG]",
       .usage = "Adjust the maximum size of a \"small file\" in bytes"
-               " (default 4096)", },
+               " (default 4K)", },
     { .name = "disable-mmap", .has_arg = 0,
       .usage = "Never mmap(2) files into the content cache", },
     { .name = "tags", .key = 'T', .has_arg = 1, .arginfo = "NAME,...",