Revert "graph.c: mark private file-scope symbols as static"

This reverts commit ba35480439.

CGit uses these symbols to output the correct HTML around graph
elements.  Making these symbols private means that CGit cannot be
updated to use Git 1.8.0 or newer, so let's not do that.

On top of the revert, also add comments so that we avoid reintroducing
this problem in the future and suggest to those modifying this API
that they might want to discuss it with the CGit developers.

Signed-off-by: John Keeping <john@keeping.me.uk>
Acked-by: Jason A. Donenfeld <Jason@zx2c4.com>
Acked-by: Johan Herland <johan@herland.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

graph.c

@@ -7,34 +7,6 @@
 
 /* Internal API */
 
-/*
- * Output the next line for a graph.
- * This formats the next graph line into the specified strbuf.  It is not
- * terminated with a newline.
- *
- * Returns 1 if the line includes the current commit, and 0 otherwise.
- * graph_next_line() will return 1 exactly once for each time
- * graph_update() is called.
- */
-static int graph_next_line(struct git_graph *graph, struct strbuf *sb);
-
-/*
- * Set up a custom scheme for column colors.
- *
- * The default column color scheme inserts ANSI color escapes to colorize
- * the graph. The various color escapes are stored in an array of strings
- * where each entry corresponds to a color, except for the last entry,
- * which denotes the escape for resetting the color back to the default.
- * When generating the graph, strings from this array are inserted before
- * and after the various column characters.
- *
- * This function allows you to enable a custom array of color escapes.
- * The 'colors_max' argument is the index of the last "reset" entry.
- *
- * This functions must be called BEFORE graph_init() is called.
- */
-static void graph_set_column_colors(const char **colors, unsigned short colors_max);
-
 /*
  * Output a padding line in the graph.
  * This is similar to graph_next_line().  However, it is guaranteed to
@@ -90,7 +62,7 @@ enum graph_state {
 static const char **column_colors;
 static unsigned short column_colors_max;
 
-static void graph_set_column_colors(const char **colors, unsigned short colors_max)
+void graph_set_column_colors(const char **colors, unsigned short colors_max)
 {
 	column_colors = colors;
 	column_colors_max = colors_max;
@@ -1144,7 +1116,7 @@ static void graph_output_collapsing_line(struct git_graph *graph, struct strbuf
 		graph_update_state(graph, GRAPH_PADDING);
 }
 
-static int graph_next_line(struct git_graph *graph, struct strbuf *sb)
+int graph_next_line(struct git_graph *graph, struct strbuf *sb)
 {
 	switch (graph->state) {
 	case GRAPH_PADDING:

graph.h

@@ -4,6 +4,25 @@
 /* A graph is a pointer to this opaque structure */
 struct git_graph;
 
+/*
+ * Set up a custom scheme for column colors.
+ *
+ * The default column color scheme inserts ANSI color escapes to colorize
+ * the graph. The various color escapes are stored in an array of strings
+ * where each entry corresponds to a color, except for the last entry,
+ * which denotes the escape for resetting the color back to the default.
+ * When generating the graph, strings from this array are inserted before
+ * and after the various column characters.
+ *
+ * This function allows you to enable a custom array of color escapes.
+ * The 'colors_max' argument is the index of the last "reset" entry.
+ *
+ * This functions must be called BEFORE graph_init() is called.
+ *
+ * NOTE: This function isn't used in Git outside graph.c but it is used
+ * by CGit (http://git.zx2c4.com/cgit/) to use HTML for colors.
+ */
+void graph_set_column_colors(const char **colors, unsigned short colors_max);
 
 /*
  * Create a new struct git_graph.
@@ -33,6 +52,20 @@ void graph_update(struct git_graph *graph, struct commit *commit);
  */
 int graph_is_commit_finished(struct git_graph const *graph);
 
+/*
+ * Output the next line for a graph.
+ * This formats the next graph line into the specified strbuf.  It is not
+ * terminated with a newline.
+ *
+ * Returns 1 if the line includes the current commit, and 0 otherwise.
+ * graph_next_line() will return 1 exactly once for each time
+ * graph_update() is called.
+ *
+ * NOTE: This function isn't used in Git outside graph.c but it is used
+ * by CGit (http://git.zx2c4.com/cgit/) to wrap HTML around graph lines.
+ */
+int graph_next_line(struct git_graph *graph, struct strbuf *sb);
+
 
 /*
  * graph_show_*: helper functions for printing to stdout