Abstract out the "name <email> date" handling of commit-tree.c

We'll want to use it for the tagging too.

ident.c

@@ -0,0 +1,138 @@
+/*
+ * ident.c
+ *
+ * create git identifier lines of the form "name <email> date"
+ *
+ * Copyright (C) 2005 Linus Torvalds
+ */
+#include "cache.h"
+
+#include <pwd.h>
+#include <time.h>
+#include <ctype.h>
+
+static char real_email[1000];
+static char real_name[1000];
+static char real_date[50];
+
+int setup_ident(void)
+{
+	int len;
+	struct passwd *pw = getpwuid(getuid());
+
+	if (!pw)
+		die("You don't exist. Go away!");
+
+	/* Get the name ("gecos") */
+	len = strlen(pw->pw_gecos);
+	if (len >= sizeof(real_name))
+		die("Your parents must have hated you");
+	memcpy(real_name, pw->pw_gecos, len+1);
+
+	/* Make up a fake email address (name + '@' + hostname [+ '.' + domainname]) */
+	len = strlen(pw->pw_name);
+	if (len > sizeof(real_email)/2)
+		die("Your parents must have hated you");
+	memcpy(real_email, pw->pw_name, len);
+	real_email[len++] = '@';
+	gethostname(real_email + len, sizeof(real_email) - len);
+	if (!strchr(real_email+len, '.')) {
+		len = strlen(real_email);
+		real_email[len++] = '.';
+		getdomainname(real_email+len, sizeof(real_email)-len);
+	}
+
+	/* And set the default date */
+	datestamp(real_date, sizeof(real_date));
+	return 0;
+}
+
+static int add_raw(char *buf, int size, int offset, const char *str)
+{
+	int len = strlen(str);
+	if (offset + len > size)
+		return size;
+	memcpy(buf + offset, str, len);
+	return offset + len;
+}
+
+static int crud(unsigned char c)
+{
+	static const char crud_array[256] = {
+		[0 ... 31] = 1,
+		[' '] = 1,
+		['.'] = 1, [','] = 1,
+		[':'] = 1, [';'] = 1,
+		['<'] = 1, ['>'] = 1,
+		['"'] = 1, ['\''] = 1,
+	};
+	return crud_array[c];
+}
+
+/*
+ * Copy over a string to the destination, but avoid special
+ * characters ('\n', '<' and '>') and remove crud at the end
+ */
+static int copy(char *buf, int size, int offset, const char *src)
+{
+	int i, len;
+	unsigned char c;
+
+	/* Remove crud from the beginning.. */
+	while ((c = *src) != 0) {
+		if (!crud(c))
+			break;
+		src++;
+	}
+
+	/* Remove crud from the end.. */
+	len = strlen(src);
+	while (len > 0) {
+		c = src[len-1];
+		if (!crud(c))
+			break;
+		--len;
+	}
+
+	/*
+	 * Copy the rest to the buffer, but avoid the special
+	 * characters '\n' '<' and '>' that act as delimeters on
+	 * a identification line
+	 */
+	for (i = 0; i < len; i++) {
+		c = *src++;
+		switch (c) {
+		case '\n': case '<': case '>':
+			continue;
+		}
+		if (offset >= size)
+			return size;
+		buf[offset++] = c;
+	}
+	return offset;
+}
+
+char *get_ident(const char *name, const char *email, const char *date_str)
+{
+	static char buffer[1000];
+	char date[50];
+	int i;
+
+	if (!name)
+		name = real_name;
+	if (!email)
+		email = real_email;
+	strcpy(date, real_date);
+	if (date_str)
+		parse_date(date_str, date, sizeof(date));
+
+	i = copy(buffer, sizeof(buffer), 0, name);
+	i = add_raw(buffer, sizeof(buffer), i, " <");
+	i = copy(buffer, sizeof(buffer), i, email);
+	i = add_raw(buffer, sizeof(buffer), i, "> ");
+	i = copy(buffer, sizeof(buffer), i, date);
+	if (i >= sizeof(buffer))
+		die("Impossibly long personal identifier");
+	buffer[i] = 0;
+	return buffer;
+}