cgit_open_filter: hand down repo configuration to script

The environment variables can be used to (for example) resolve
the following situation:

Suppose a server setup in which each repository has a trac
instance; the commit filter needs to know with which
repository it's dealing in order to be able to resolve the
#123 ticket numbers in the commit messages into hyperlinks
into the correct trac instance.

Signed-off-by: Ferry Huberts <ferry.huberts@pelagic.nl>
Signed-off-by: Lars Hjemli <hjemli@gmail.com>

1 files changed, 77 insertions, 1 deletions

diff --git a/shared.c b/shared.c
index e4879df..8c3d18a 100644
--- a/shared.c
+++ b/shared.c
@@ -7,6 +7,8 @@
  */
 
 #include "cgit.h"
+#include <stdio.h>
+#include <linux/limits.h>
 
 struct cgit_repolist cgit_repolist;
 struct cgit_context ctx;
@@ -376,6 +378,70 @@ int cgit_parse_snapshots_mask(const char *str)
         return rv;
 }
 
+typedef struct {
+        char * name;
+        char * value;
+} cgit_env_var;
+
+static char * prepare_env(struct cgit_repo * repo) {
+        cgit_env_var env_vars[] = {
+                { .name = "CGIT_REPO_URL", .value = repo->url },
+                { .name = "CGIT_REPO_NAME", .value = repo->name },
+                { .name = "CGIT_REPO_PATH", .value = repo->path },
+                { .name = "CGIT_REPO_OWNER", .value = repo->owner },
+                { .name = "CGIT_REPO_DEFBRANCH", .value = repo->defbranch },
+                { .name = "CGIT_REPO_SECTION", .value = repo->section },
+                { .name = "CGIT_REPO_CLONE_URL", .value = repo->clone_url }
+        };
+        int env_var_count = ARRAY_SIZE(env_vars);
+        long values_space = (env_var_count * (PATH_MAX + 64));
+
+        void * buffer;
+        char ** vars;
+        char * values;
+        int vars_index = 0;
+        unsigned int chars_printed;
+
+        /* Allocate buffer for environment variables: first in the buffer is an
+         * array of pointers to argument strings, terminated with a NULL pointer.
+         * After that the argument strings are placed after each other */
+        buffer = malloc(((env_var_count + 1) * sizeof(char *)) + values_space);
+        if (!buffer)
+                return NULL;
+
+        vars = buffer;
+        values = (char *) &vars[env_var_count + 1];
+
+        /* loop over all defined environment variables and their values */
+        while (vars_index < env_var_count) {
+                char * name = env_vars[vars_index].name;
+                char * value = env_vars[vars_index].value;
+
+                if (!value)
+                        value = "";
+
+                chars_printed = snprintf(values, (values_space - 1), "%s=%s", name,
+                                value);
+                if (chars_printed > (values_space - 1)) {
+                        /* Buffer space exhausted: stop adding variables.
+                         * Not all environment variables are defined, but the best we can
+                         * do is to provide the ones that _are_ defined */
+                        break;
+                }
+
+                values[chars_printed] = '\0';
+                *&vars[vars_index] = values;
+                values += (chars_printed + 1);
+                values_space -= (chars_printed + 1);
+                vars_index++;
+        }
+
+        /* terminate the array with pointers */
+        *&vars[vars_index] = NULL;
+
+        return (char *) buffer;
+}
+
 int cgit_open_filter(struct cgit_filter *filter, struct cgit_repo * repo)
 {
 
@@ -384,10 +450,20 @@ int cgit_open_filter(struct cgit_filter *filter, struct cgit_repo * repo)
         chk_zero(pipe(filter->pipe_fh), "Unable to create pipe to subprocess");
         filter->pid = chk_non_negative(fork(), "Unable to create subprocess");
         if (filter->pid == 0) {
+                char * env = NULL;
+
                 close(filter->pipe_fh[1]);
                 chk_non_negative(dup2(filter->pipe_fh[0], STDIN_FILENO),
                         "Unable to use pipe as STDIN");
-                execvp(filter->cmd, filter->argv);
+
+                if (repo)
+                        env = prepare_env(repo);
+
+                execve(filter->cmd, filter->argv, (char **)env);
+
+                if (env)
+                        free(env);
+
                 die("Unable to exec subprocess %s: %s (%d)", filter->cmd,
                         strerror(errno), errno);
         }