Cosmetic improvements for options-handling code in ECPGconnect().

The comment describing the string format was a lie.  Make it agree with
reality, add/improve some other comments, fix coding style for loops with
empty bodies.  Also add an Assert that we counted parameters correctly,
because the spread-out logic for that looks pretty fragile.

No actual bugs fixed here, so no need to back-patch.

Discussion: https://postgr.es/m/848B1649C8A6274AA527C4472CA11EDD5FC70CBE@G01JPEXMBYT02

src/interfaces/ecpg/ecpglib/connect.c

@@ -516,9 +516,9 @@ ECPGconnect(int lineno, int c, const char *name, const char *user, const char *p
 			 options ? "with options " : "", options ? options : "",
 			 (user && strlen(user) > 0) ? "for user " : "", user ? user : "");
 
+	/* count options (this may produce an overestimate, it's ok) */
 	if (options)
 		for (i = 0; options[i]; i++)
-			/* count options */
 			if (options[i] == '=')
 				connect_params++;
 
@@ -585,8 +585,12 @@ ECPGconnect(int lineno, int c, const char *name, const char *user, const char *p
 	{
 		char	   *str;
 
-		/* options look like this "option1 = value1 option2 = value2 ... */
-		/* we have to break up the string into single options */
+		/*
+		 * The options string contains "keyword=value" pairs separated by
+		 * '&'s.  We must break this up into keywords and values to pass to
+		 * libpq (it's okay to scribble on the options string).  We ignore
+		 * spaces just before each keyword or value.
+		 */
 		for (str = options; *str;)
 		{
 			int			e,
@@ -594,13 +598,21 @@ ECPGconnect(int lineno, int c, const char *name, const char *user, const char *p
 			char	   *token1,
 					   *token2;
 
-			for (token1 = str; *token1 && *token1 == ' '; token1++);
-			for (e = 0; token1[e] && token1[e] != '='; e++);
+			/* Skip spaces before keyword */
+			for (token1 = str; *token1 == ' '; token1++)
+				 /* skip */ ;
+			/* Find end of keyword */
+			for (e = 0; token1[e] && token1[e] != '='; e++)
+				 /* skip */ ;
 			if (token1[e])		/* found "=" */
 			{
 				token1[e] = '\0';
-				for (token2 = token1 + e + 1; *token2 && *token2 == ' '; token2++);
-				for (a = 0; token2[a] && token2[a] != '&'; a++);
+				/* Skip spaces before value */
+				for (token2 = token1 + e + 1; *token2 == ' '; token2++)
+					 /* skip */ ;
+				/* Find end of value */
+				for (a = 0; token2[a] && token2[a] != '&'; a++)
+					 /* skip */ ;
 				if (token2[a])	/* found "&" => another option follows */
 				{
 					token2[a] = '\0';
@@ -614,11 +626,14 @@ ECPGconnect(int lineno, int c, const char *name, const char *user, const char *p
 				i++;
 			}
 			else
-				/* the parser should not be able to create this invalid option */
+			{
+				/* Bogus options syntax ... ignore trailing garbage */
 				str = token1 + e;
 			}
-
 		}
+	}
+
+	Assert(i <= connect_params);
 	conn_keywords[i] = NULL;	/* terminator */
 
 	this->connection = PQconnectdbParams(conn_keywords, conn_values, 0);