Save username -> Full Name <email@addr.es> map file

When the user specifies a username -> Full Name <email@addr.es> map
file with the -A option, save a copy of that file as
$git_dir/svn-authors. When running git-svnimport with an existing GIT
directory, use $git_dir/svn-authors (if it exists) unless a file was
explicitly specified with -A.

Signed-off-by: Karl Hasselström <kha@treskal.com>
Signed-off-by: Junio C Hamano <junkio@cox.net>

Documentation/git-svnimport.txt

@@ -82,6 +82,11 @@ When importing incrementally, you might need to edit the .git/svn2git file.
 	"username". If encountering a commit made by a user not in the
 	list, abort.
 
+	For convenience, this data is saved to $GIT_DIR/svn-authors
+	each time the -A option is provided, and read from that same
+	file each time git-svnimport is run with an existing GIT
+	repository without -A.
+
 -m::
 	Attempt to detect merges based on the commit message. This option
 	will enable default regexes that try to capture the name source

git-svnimport.perl

@@ -13,6 +13,7 @@
 use strict;
 use warnings;
 use Getopt::Std;
+use File::Copy;
 use File::Spec;
 use File::Temp qw(tempfile);
 use File::Path qw(mkpath);
@@ -68,10 +69,16 @@ END
 	push (@mergerx, qr/$opt_M/);
 }
 
+# Absolutize filename now, since we will have chdir'ed by the time we
+# get around to opening it.
+$opt_A = File::Spec->rel2abs($opt_A) if $opt_A;
+
 our %users = ();
-if ($opt_A) {
-	die "Cannot open $opt_A\n" unless -f $opt_A;
-	open(my $authors,$opt_A);
+our $users_file = undef;
+sub read_users($) {
+	$users_file = File::Spec->rel2abs(@_);
+	die "Cannot open $users_file\n" unless -f $users_file;
+	open(my $authors,$users_file);
 	while(<$authors>) {
 		chomp;
 		next unless /^(\S+?)\s*=\s*(.+?)\s*<(.+)>\s*$/;
@@ -302,6 +309,14 @@ ($$)
 -d $git_dir
 	or die "Could not create git subdir ($git_dir).\n";
 
+my $default_authors = "$git_dir/svn-authors";
+if ($opt_A) {
+	read_users($opt_A);
+	copy($opt_A,$default_authors) or die "Copy failed: $!";
+} else {
+	read_users($default_authors) if -f $default_authors;
+}
+
 open BRANCHES,">>", "$git_dir/svn2git";
 
 sub node_kind($$$) {
@@ -498,8 +513,8 @@ sub commit {
 
 	if (not defined $author) {
 		$author_name = $author_email = "unknown";
-	} elsif ($opt_A) {
-		die "User $author is not listed in $opt_A\n"
+	} elsif (defined $users_file) {
+		die "User $author is not listed in $users_file\n"
 		    unless exists $users{$author};
 		($author_name,$author_email) = @{$users{$author}};
 	} elsif ($author =~ /^(.*?)\s+<(.*)>$/) {