Re: [PATCH 04/10] evolve: add support for parsing metacommits

> > This patch adds the get_metacommit_content method, which can classify
> > commits as either metacommits or normal commits, determine whether they
> > are abandoned, and extract the content commit's object id from the
> > metacommit.
> > diff --git a/Makefile b/Makefile
> > index cac3452edb9..b2bcc00c289 100644
> > --- a/Makefile
> > +++ b/Makefile
> > @@ -999,6 +999,7 @@ LIB_OBJS += merge-ort.o
> >   LIB_OBJS += merge-ort-wrappers.o
> >   LIB_OBJS += merge-recursive.o
> >   LIB_OBJS += merge.o
> > +LIB_OBJS += metacommit-parser.o
>
> There seems to be a problem with the indent here

>
> >   LIB_OBJS += midx.o
> >   LIB_OBJS += name-hash.o
> >   LIB_OBJS += negotiator/default.o
>
>  > diff --git a/metacommit-parser.h b/metacommit-parser.h
>  > new file mode 100644
>  > index 00000000000..1c74bd6d699
>  > --- /dev/null
>  > +++ b/metacommit-parser.h
>  > @@ -0,0 +1,19 @@
>  > +#ifndef METACOMMIT_PARSER_H
>  > +#define METACOMMIT_PARSER_H
>  > +
>  > +#include "commit.h"
>  > +#include "hash.h"
>  > +
>  > +/* Indicates a normal commit (non-metacommit) */
>  > +#define METACOMMIT_TYPE_NONE 0
>  > +/* Indicates a metacommit with normal content (non-abandoned) */
>  > +#define METACOMMIT_TYPE_NORMAL 1
>  > +/* Indicates a metacommit with abandoned content */
>  > +#define METACOMMIT_TYPE_ABANDONED 2
>
> Is it possible to define these as an enum? It would make the signature
> of get_meta_commit_content() nicer.
>
>  > +struct commit;
>
> What's this for? We're including commit.h above.

>
>  > +extern int get_metacommit_content(
>  > +    struct commit *commit, struct object_id *content);
>
> > diff --git a/metacommit-parser.c b/metacommit-parser.c
> > new file mode 100644
> > index 00000000000..70c1428bfc6
> > --- /dev/null
> > +++ b/metacommit-parser.c
> > @@ -0,0 +1,110 @@
> > +#include "cache.h"
> > +#include "metacommit-parser.h"
> > +#include "commit.h"
> > +
> > +/*
> > + * Search the commit buffer for a line starting with the given key. Unlike
> > + * find_commit_header, this also searches the commit message body.
> > + */
>
> There is no explanation in the code or commit message as to why this
> function is needed. The documentation added in the first commit says
> that "parent-type" header is a commit header. I think the answer is that
> this series does not implement that header but uses the commit message
> instead. That's perfectly fine for a proof of concept but it is
> precisely the sort of detail that should be described it the commit
> message and probably flagged up in the cover letter.

>
> > +static const char *find_key(const char *msg, const char *key, size_t *out_len)
> > +{
> > +     int key_len = strlen(key);
> > +     const char *line = msg;
> > +
> > +     while (line) {
> > +             const char *eol = strchrnul(line, '\n');
> > +
> > +             if (eol - line > key_len && !memcmp(line, key, key_len) &&
> > +                 line[key_len] == ' ') {
> > +                     *out_len = eol - line - key_len - 1;
> > +                     return line + key_len + 1;
> > +             }
> > +             line = *eol ? eol + 1 : NULL;
> > +     }
> > +     return NULL;
> > +}
> > +
> > +static struct commit *get_commit_by_index(struct commit_list *to_search, int index)
> > +{
> > +     while (to_search && index) {
> > +             to_search = to_search->next;
> > +             index--;
> > +     }
> > +
> > +     if (!to_search)
> > +             return NULL;
> > +
> > +     return to_search->item;
> > +}
>
> This function is a useful utility for struct commit_list and should live
> in commit.c. It could be used to simplify object-name.c:get_parent() for
> example.

>
> > +/*
> > + * Writes the index of the content parent to "result". Returns the metacommit
> > + * type. See the METACOMMIT_TYPE_* constants.
> > + */
> > +static int index_of_content_commit(const char *buffer, int *result)
>
> I found the signature confusing as it is returning an int but that is
> not the index. Switching to an enum for the metacommit types would
> clarify that.

>
> > +{
> > +     int index = 0;
> > +     int ret = METACOMMIT_TYPE_NONE;
> > +     size_t parent_types_size;
> > +     const char *parent_types = find_key(buffer, "parent-type",
> > +             &parent_types_size);
> > +     const char *end;
> > +     const char *enum_start = parent_types;
> > +     int enum_length = 0;
> > +
> > +     if (!parent_types)
> > +             return METACOMMIT_TYPE_NONE;
> > +
> > +     end = &parent_types[parent_types_size];
> > +
> > +     while (1) {
> > +             char next = *parent_types;
> > +             if (next == ' ' || parent_types >= end) {
> > +                     if (enum_length == 1) {
>
> if enum_length != 1 then there is an error in the parent-type header and
> we should probably bail out.
>
> > +                             char first_char_in_enum = *enum_start;
>
> It's not just the first character, it's the only character, do we really
> need such a long variable name? (how about just calling it "type")