Re: [GSoC][PATCH 08/13] submodule: port submodule subcommand 'summary' from shell to C

The submodule subcommand 'summary' is ported in the process of
making git-submodule a builtin. The function cmd_summary() from
git-submodule.sh is ported to functions module_summary(),
compute_summary_module_list(), prepare_submodule_summary() and
print_submodule_summary().

The first function module_summary() parses the options of submodule
subcommand and also acts as the front-end of this subcommand.
After parsing them, it calls the compute_summary_module_list()

The functions compute_summary_module_list() runs the diff_cmd,
and generates the modules list, as required by the subcommand.
The generation of this module list is done by the using the
callback function submodule_summary_callback(), and stored in the
structure module_cb.

Once the module list is generated, prepare_submodule_summary()
further goes through the list and filters the list, for
eventually calling the print_submodule_summary() function.

Finally, the print_submodule_summary() takes care of generating
and printing the summary for each submodule.

Mentored-by: Christian Couder [off-list ref]
Mentored-by: Stefan Beller [off-list ref]
Signed-off-by: Prathamesh Chavan <redacted>
---
In this new version, the following changes have been made:

* Firstly, about the function compute_summary_module_list().
  This function is created to generate the list of modules, for which
  we will generate the summary further. Since the list is actually
  generated using the git-diff-files or git-diff-index command, but for
  porting this, we required to create a function similar to the builtin
  functions of the above commands. But we can't directly call cmd_diff_files()
  and cmd_diff_index() since we don't have to display the output and instead
  need to store it. Hence, this function is introduced.

* Also, the module_cb_list *list is not freed since it is a non-heap object.
  Hence, free() can't be using on the non-heap objects.

* In the function prepare_submodule_summary(), as suggested
  'git_config_get_string_const' was used instead of instead of '_value'

* Some variables which weren't modified throughout the function-call were
  passed as const.

* The '!!' trick, which wasn't used in the last patch, is now used in this
  new version .

* the variables sha1_dst and sha1_src are removed from the function
  print_submodule_summary(), and instead the p->oid_src and p->oid_dst are
  used.

* The variable sm_git_dir is freed at the end of the function.

* variable head was no longer used in module_summary() and instead the strbuf
  was utilized.

 builtin/submodule--helper.c | 425 ++++++++++++++++++++++++++++++++++++++++++++
 git-submodule.sh            | 182 +------------------
 2 files changed, 426 insertions(+), 181 deletions(-)

diff --git a/builtin/submodule--helper.c b/builtin/submodule--helper.c
index f642f9889..94438d6ce 100644
--- a/builtin/submodule--helper.c
+++ b/builtin/submodule--helper.c

@@ -13,6 +13,9 @@
 #include "remote.h"
 #include "refs.h"
 #include "connect.h"
+#include "revision.h"
+#include "diffcore.h"
+#include "diff.h"

 typedef void (*submodule_list_func_t)(const struct cache_entry *list_item,
                                      void *cb_data);

@@ -766,6 +769,427 @@ static int module_name(int argc, const char **argv, const char *prefix)
        return 0;
 }

+struct module_cb {
+       unsigned int mod_src;
+       unsigned int mod_dst;
+       struct object_id oid_src;
+       struct object_id oid_dst;
+       char status;
+       const char *sm_path;
+};
+#define MODULE_CB_INIT { 0, 0, NULL, NULL, '\0', NULL }
+
+struct module_cb_list {
+       struct module_cb **entries;
+       int alloc, nr;
+};
+#define MODULE_CB_LIST_INIT { NULL, 0, 0 }
+
+struct summary_cb {
+       int argc;
+       const char **argv;
+       const char *prefix;
+       char *diff_cmd;
+       unsigned int cached: 1;
+       unsigned int for_status: 1;
+       unsigned int quiet: 1;
+       unsigned int files: 1;
+       int summary_limits;
+};
+#define SUMMARY_CB_INIT { 0, NULL, NULL, NULL, 0, 0, 0, 0, 0 }
+
+static int verify_submodule_object_name(const char *sm_path, const char *sha1)
+{
+       struct child_process cp_rev_parse = CHILD_PROCESS_INIT;
+
+       cp_rev_parse.git_cmd = 1;
+       cp_rev_parse.no_stdout = 1;
+       cp_rev_parse.dir = sm_path;
+       prepare_submodule_repo_env(&cp_rev_parse.env_array);
+
+       argv_array_pushl(&cp_rev_parse.args, "rev-parse", "-q",
+                        "--verify", NULL);
+       argv_array_pushf(&cp_rev_parse.args, "%s^0", sha1);
+
+       if (run_command(&cp_rev_parse))
+               return 1;
+
+       return 0;
+}
+
+static void print_submodule_summary(struct summary_cb *info,
+                                   struct module_cb *p)
+{
+       int missing_src = 0;
+       int missing_dst = 0;
+       char *displaypath;
+       const char *sha1_abbr_src;
+       const char *sha1_abbr_dst;
+       int errmsg = 0;
+       int total_commits = -1;
+       char *sm_git_dir = xstrfmt("%s/.git", p->sm_path);
+       int is_sm_git_dir = 0;
+
+       if (!info->cached && !oidcmp(&p->oid_dst, &null_oid)) {
+               if (S_ISGITLINK(p->mod_dst)) {
+                       struct child_process cp_rev_parse = CHILD_PROCESS_INIT;
+                       struct strbuf sb_rev_parse = STRBUF_INIT;
+
+                       cp_rev_parse.git_cmd = 1;
+                       cp_rev_parse.no_stderr = 1;
+                       cp_rev_parse.dir = p->sm_path;
+                       prepare_submodule_repo_env(&cp_rev_parse.env_array);
+
+                       argv_array_pushl(&cp_rev_parse.args,
+                                        "rev-parse", "HEAD", NULL);
+                       if (!capture_command(&cp_rev_parse, &sb_rev_parse, 0)) {
+                               strbuf_strip_suffix(&sb_rev_parse, "\n");
+
+                               get_oid_hex(sb_rev_parse.buf, &p->oid_dst);
+                       }
+                       strbuf_release(&sb_rev_parse);