badwords: check indented lines in source code, fix fallouts

- badwords.pl: add `-a` option to check all lines in source code files.
  Before this patch indented lines were skipped (to avoid Markdown code
  fences.)
- GHA/checksrc: use `-a` when verifying the source code.
- GHA/checksrc: disable `So` and `But` rules for source code.
- GHA/checksrc: add docs/examples to the verified sources.
- badwords.txt: delete 4 duplicates.
- badwords.txt: group and sort contractions.
- badwords.txt: allow ` url = `, `DIR`, `<file name`.

Closes #19536

src/config2setopts.c

@@ -212,11 +212,11 @@ static CURLcode ssh_setopts(struct OperationConfig *config, CURL *curl)
       config->knownhosts = known;
     }
     else if(!config->hostpubmd5 && !config->hostpubsha256) {
-      errorf("Couldn't find a known_hosts file");
+      errorf("Could not find a known_hosts file");
       return CURLE_FAILED_INIT;
     }
     else
-      warnf("Couldn't find a known_hosts file");
+      warnf("Could not find a known_hosts file");
   }
   return CURLE_OK; /* ignore if SHA256 did not work */
 }

src/tool_cb_rea.c

@@ -60,7 +60,7 @@ static bool waitfd(int waitms, int fd)
   struct timeval timeout;
 
   if(fd >= FD_SETSIZE)
-    /* can't wait! */
+    /* cannot wait! */
     return FALSE;
 
   /* wait this long at the most */

src/tool_cb_see.c

@@ -55,8 +55,8 @@ int tool_seek_cb(void *userdata, curl_off_t offset, int whence)
 
   if(offset > OUR_MAX_SEEK_O) {
     /* Some precaution code to work around problems with different data sizes
-       to allow seeking >32-bit even if off_t is 32-bit. Should be very rare
-       and is really valid on weirdo-systems. */
+       to allow seeking >32-bit even if off_t is 32-bit. Should be rare and
+       is really valid on weirdo-systems. */
     curl_off_t left = offset;
 
     if(whence != SEEK_SET)

src/tool_doswin.c

@@ -874,7 +874,7 @@ curl_socket_t win32_stdin_read_thread(void)
       break;
     }
 
-    /* Start up the thread. We don't bother keeping a reference to it
+    /* Start up the thread. We do not bother keeping a reference to it
        because it runs until program termination. From here on out all reads
        from the stdin handle or file descriptor 0 will be reading from the
        socket that is fed by the thread. */

src/tool_getparam.c

@@ -1213,7 +1213,7 @@ static ParameterError parse_ech(struct OperationConfig *config,
         file = curlx_fopen(nextarg, FOPEN_READTEXT);
       }
       if(!file) {
-        warnf("Couldn't read file \"%s\" "
+        warnf("Could not read file \"%s\" "
               "specified for \"--ech ecl:\" option",
               nextarg);
         return PARAM_BAD_USE; /*  */
@@ -2084,7 +2084,7 @@ static ParameterError opt_bool(struct OperationConfig *config,
     config->doh_insecure_ok = toggle;
     break;
   case C_LIST_ONLY: /* --list-only */
-    config->dirlistonly = toggle; /* only list the names of the FTP dir */
+    config->dirlistonly = toggle; /* only list names of the FTP directory */
     break;
   case C_MANUAL: /* --manual */
     if(toggle)   /* --no-manual shows no manual... */
@@ -2876,7 +2876,7 @@ ParameterError getparameter(const char *flag, /* f or -long-flag */
     /* is there an '=' ? */
     if(!curlx_str_until(&p, &out, MAX_OPTION_LEN, '=') &&
        !curlx_str_single(&p, '=') ) {
-      /* there's an equal sign */
+      /* there is an equal sign */
       char tempword[MAX_OPTION_LEN + 1];
       memcpy(tempword, curlx_str(&out), curlx_strlen(&out));
       tempword[curlx_strlen(&out)] = 0;

src/tool_operate.c

@@ -2252,7 +2252,7 @@ CURLcode operate(int argc, argv_item_t argv[])
       strcmp(first_arg, "--disable"))) {
     parseconfig(NULL, CONFIG_MAX_LEVELS); /* ignore possible failure */
 
-    /* If we had no arguments then make sure a url was specified in .curlrc */
+    /* If we had no arguments then make sure a URL was specified in .curlrc */
     if((argc < 2) && (!global->first->url_list)) {
       helpf(NULL);
       result = CURLE_FAILED_INIT;

src/tool_operhlp.c

@@ -211,7 +211,7 @@ CURLcode get_url_file_name(char **filename, const char *url)
       else {
         /* no slash => empty string, use default */
         *filename = strdup("curl_response");
-        warnf("No remote file name, uses \"%s\"", *filename);
+        warnf("No remote filename, uses \"%s\"", *filename);
       }
 
       curl_free(path);

src/tool_paramhlp.c

@@ -135,7 +135,7 @@ ParameterError file2memory_range(char **bufp, size_t *size, FILE *file,
         offset = starto;
       }
       else
-        /* we can't seek stdin, read 'starto' bytes and throw them away */
+        /* we cannot seek stdin, read 'starto' bytes and throw them away */
         throwaway = starto;
     }
 

src/tool_parsecfg.c

@@ -103,7 +103,7 @@ ParameterError parseconfig(const char *filename, int max_recursive)
 #if defined(_WIN32) && !defined(UNDER_CE)
     else {
       char *fullp;
-      /* check for .curlrc then _curlrc in the dir of the executable */
+      /* check for .curlrc then _curlrc in the directory of the executable */
       file = tool_execpath(".curlrc", &fullp);
       if(!file)
         file = tool_execpath("_curlrc", &fullp);