[RFCv2 09/12] Teach foreign transport code to perform the "capabilities" command

The features reported by the vcs helper are stored in the foreign_data struct
which is expanded for this purpose.

In the process, we also change the capabilities command slightly to expect
one feature per line (instead of all features on a single line). This enables
us to add features in the future that take one or more arguments. To terminate
the list of features, a blank line is output at the end.

Signed-off-by: Johan Herland <johan@xxxxxxxxxxx>
---
 Documentation/git-vcs.txt |    8 ++--
 transport-foreign.c       |   83 ++++++++++++++++++++++++++++++++++-----------
 2 files changed, 67 insertions(+), 24 deletions(-)

diff --git a/Documentation/git-vcs.txt b/Documentation/git-vcs.txt
index febe415..85656d4 100644
--- a/Documentation/git-vcs.txt
+++ b/Documentation/git-vcs.txt
@@ -33,10 +33,10 @@ The output of each command must be produced on the helper's 
standard output.
 The helper's standard error stream can be used for status/progress messages.
 
 'capabilities'::
-       Outputs a single line with a list of feature names separated
-       by spaces. Each of these indicates a supported feature of the
-       helper, and the caller will only attempt operations that are
-       supported.
+       Outputs a list of feature names, one per line. Each of these
+       indicates a supported feature of the helper, and the caller
+       will only attempt operations that are supported.
+       The output list shall be terminated with a blank line.
 
 'list'::
        Outputs the names of refs, one per line. These may be
diff --git a/transport-foreign.c b/transport-foreign.c
index 29aad77..be0a587 100644
--- a/transport-foreign.c
+++ b/transport-foreign.c
@@ -8,38 +8,81 @@
 
 struct foreign_data
 {
-       struct child_process *importer;
+       struct child_process importer;
+
+       /* capabilities */
+       unsigned export:1;
+       unsigned export_branch:1;
+       unsigned export_merges:1;
 };
 
+static void get_foreign_capabilities(struct foreign_data *fdata)
+{
+       struct strbuf buf;
+       FILE *file;
+
+       write(fdata->importer.in, "capabilities\n", 13);
+
+       strbuf_init(&buf, 0);
+       file = fdopen(fdata->importer.out, "r");
+       while (1) {
+               char *eon;
+               if (strbuf_getline(&buf, file, '\n') == EOF)
+                       break;
+
+               if (!*buf.buf)
+                       break;
+
+               eon = strchr(buf.buf, ' ');
+               if (eon)
+                       *eon = '\0';
+
+               /* parse features */
+               if (!strcmp(buf.buf, "export"))
+                       fdata->export = 1;
+               else if (!strcmp(buf.buf, "export-branch"))
+                       fdata->export_branch = 1;
+               else if (!strcmp(buf.buf, "export-merges"))
+                       fdata->export_merges = 1;
+               else
+                       die("Invalid feature '%s'", buf.buf);
+
+               strbuf_reset(&buf);
+       }
+
+       strbuf_release(&buf);
+}
+
 static struct child_process *get_importer(struct transport *transport)
 {
-       struct child_process *importer = transport->data;
-       if (!importer) {
+       struct foreign_data *fdata = (struct foreign_data *) transport->data;
+       if (!fdata) {
                struct strbuf buf;
-               importer = xcalloc(1, sizeof(*importer));
-               importer->in = -1;
-               importer->out = -1;
-               importer->err = 0;
-               importer->argv = xcalloc(3, sizeof(*importer->argv));
+               fdata = xcalloc(1, sizeof(*fdata));
+               fdata->importer.in = -1;
+               fdata->importer.out = -1;
+               fdata->importer.err = 0;
+               fdata->importer.argv = xcalloc(3, 
sizeof(*fdata->importer.argv));
                strbuf_init(&buf, 80);
                strbuf_addf(&buf, "vcs-%s", transport->remote->foreign_vcs);
-               importer->argv[0] = buf.buf;
-               importer->argv[1] = transport->remote->name;
-               importer->git_cmd = 1;
-               start_command(importer);
-               transport->data = importer;
+               fdata->importer.argv[0] = buf.buf;
+               fdata->importer.argv[1] = transport->remote->name;
+               fdata->importer.git_cmd = 1;
+               start_command(&fdata->importer);
+               get_foreign_capabilities(fdata);
+               transport->data = fdata;
        }
-       return importer;
+       return &fdata->importer;
 }
 
 static int disconnect_foreign(struct transport *transport)
 {
-       struct child_process *importer = transport->data;
-       if (importer) {
-               write(importer->in, "\n", 1);
-               close(importer->in);
-               finish_command(importer);
-               free(importer);
+       struct foreign_data *fdata = (struct foreign_data *) transport->data;
+       if (fdata) {
+               write(fdata->importer.in, "\n", 1);
+               close(fdata->importer.in);
+               finish_command(&fdata->importer);
+               free(fdata);
                transport->data = NULL;
        }
        return 0;
-- 
1.6.4.rc3.138.ga6b98.dirty

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