psql: Add variable to control keyword case in tab completion

This adds the variable COMP_KEYWORD_CASE, which controls in what case
keywords are completed.  This is partially to let users configure the
change from commit 69f4f1c3, but it
also offers more behaviors than were available before.

doc/src/sgml/ref/psql-ref.sgml

@@ -2656,6 +2656,22 @@ bar
         </listitem>
       </varlistentry>
 
+      <varlistentry>
+        <term><varname>COMP_KEYWORD_CASE</varname></term>
+        <listitem>
+        <para>
+        Determines which letter case to use when completing an SQL key word.
+        If set to <literal>lower</literal> or <literal>upper</literal>, the
+        completed word will be in lower or upper case, respectively.  If set
+        to <literal>preserve-lower</literal>
+        or <literal>preserve-upper</literal> (the default), the completed word
+        will be in the case of the word already entered, but words being
+        completed without anything entered will be in lower or upper case,
+        respectively.
+        </para>
+        </listitem>
+      </varlistentry>
+
       <varlistentry>
         <term><varname>DBNAME</varname></term>
         <listitem>

src/bin/psql/tab-complete.c

@@ -697,7 +697,7 @@ static char **complete_from_variables(char *text,
 						const char *prefix, const char *suffix);
 static char *complete_from_files(const char *text, int state);
 
-static char *pg_strdup_same_case(const char *s, const char *ref);
+static char *pg_strdup_keyword_case(const char *s, const char *ref);
 static PGresult *exec_query(const char *query);
 
 static void get_previous_words(int point, char **previous_words, int nwords);
@@ -3125,7 +3125,7 @@ create_or_drop_command_generator(const char *text, int state, bits32 excluded)
 	{
 		if ((pg_strncasecmp(name, text, string_length) == 0) &&
 			!(words_after_create[list_index - 1].flags & excluded))
-			return pg_strdup_same_case(name, text);
+			return pg_strdup_keyword_case(name, text);
 	}
 	/* if nothing matches, return NULL */
 	return NULL;
@@ -3412,9 +3412,9 @@ complete_from_list(const char *text, int state)
 			if (completion_case_sensitive)
 				return pg_strdup(item);
 			else
-				/* If case insensitive matching was requested initially, return
-				 * it in the case of what was already entered. */
-				return pg_strdup_same_case(item, text);
+				/* If case insensitive matching was requested initially, adjust
+				 * the case according to setting. */
+				return pg_strdup_keyword_case(item, text);
 		}
 	}
 
@@ -3451,9 +3451,9 @@ complete_from_const(const char *text, int state)
 		if (completion_case_sensitive)
 			return pg_strdup(completion_charp);
 		else
-			/* If case insensitive matching was requested initially, return it
-			 * in the case of what was already entered. */
-			return pg_strdup_same_case(completion_charp, text);
+			/* If case insensitive matching was requested initially, adjust the
+			 * case according to setting. */
+			return pg_strdup_keyword_case(completion_charp, text);
 	}
 	else
 		return NULL;
@@ -3561,27 +3561,48 @@ complete_from_files(const char *text, int state)
 
 
 /*
- * Make a pg_strdup copy of s and convert it to the same case as ref.
+ * Make a pg_strdup copy of s and convert the case according to
+ * COMP_KEYWORD_CASE variable, using ref as the text that was already entered.
  */
 static char *
-pg_strdup_same_case(const char *s, const char *ref)
+pg_strdup_keyword_case(const char *s, const char *ref)
 {
 	char *ret, *p;
 	unsigned char first = ref[0];
+	int		tocase;
+	const char *varval;
+
+	varval = GetVariable(pset.vars, "COMP_KEYWORD_CASE");
+	if (!varval)
+		tocase = 0;
+	else if (strcmp(varval, "lower") == 0)
+		tocase = -2;
+	else if (strcmp(varval, "preserve-lower") == 0)
+		tocase = -1;
+	else if (strcmp(varval, "preserve-upper") == 0)
+		tocase = +1;
+	else if (strcmp(varval, "upper") == 0)
+		tocase = +2;
+	else
+		tocase = 0;
 
-	if (isalpha(first))
-	{
-		ret = pg_strdup(s);
-		if (islower(first))
-			for (p = ret; *p; p++)
-				*p = pg_tolower((unsigned char) *p);
-		else
-			for (p = ret; *p; p++)
-				*p = pg_toupper((unsigned char) *p);
-		return ret;
-	}
+	/* default */
+	if (tocase == 0)
+		tocase = +1;
+
+	ret = pg_strdup(s);
+
+	if (tocase == -2
+		|| ((tocase == -1 || tocase == +1) && islower(first))
+		|| (tocase == -1 && !isalpha(first))
+		)
+		for (p = ret; *p; p++)
+			*p = pg_tolower((unsigned char) *p);
 	else
-		return pg_strdup(s);
+		for (p = ret; *p; p++)
+			*p = pg_toupper((unsigned char) *p);
+
+	return ret;
 }