Re: [PATCH v3 37/44] refs: break out a ref conflict check

[Michael Haggerty]

On 10/12/2015 11:51 PM, David Turner wrote:
> Create new function verify_no_descendants, to hold one of the ref
> conflict checks used in verify_refname_available.  Multiple backends
> will need this function, so it goes in the common code.
> 
> Signed-off-by: David Turner 
> ---
>  refs-be-files.c | 33 -
>  refs.c  | 22 ++
>  refs.h  |  7 +++
>  3 files changed, 37 insertions(+), 25 deletions(-)
> 
> [...]
> diff --git a/refs.c b/refs.c
> index 5a3125d..3ae0274 100644
> --- a/refs.c
> +++ b/refs.c
> @@ -1101,6 +1101,28 @@ enum peel_status peel_object(const unsigned char 
> *name, unsigned char *sha1)
>   return PEEL_PEELED;
>  }
>  
> +const char *find_descendant_ref(const char *refname,
> + const struct string_list *extras,
> + const struct string_list *skip)
> +{
> + int pos;
> + if (!extras)
> + return NULL;
> +
> + /* Look for the place where "$refname/" would be inserted in extras. */

The comment above is misleading. See my note at the bottom of this email
for an explanation.

> + for (pos = string_list_find_insert_index(extras, refname, 0);
> +  pos < extras->nr; pos++) {
> + const char *extra_refname = extras->items[pos].string;
> +
> + if (!starts_with(extra_refname, refname))
> + break;
> +
> + if (!skip || !string_list_has_string(skip, extra_refname))
> + return extra_refname;
> + }
> + return NULL;
> +}
> +
>  /* backend functions */
>  int refs_initdb(struct strbuf *err, int shared)
>  {
> diff --git a/refs.h b/refs.h
> index 3aad3b8..f8becea 100644
> --- a/refs.h
> +++ b/refs.h
> @@ -637,6 +637,13 @@ int files_log_ref_write(const char *refname, const 
> unsigned char *old_sha1,
>   const unsigned char *new_sha1, const char *msg,
>   int flags, struct strbuf *err);
>  
> +/*
> + * Check for entries in extras that start with "$refname/", ignoring
> + * those in skip. If there is such an entry, then we have a conflict.
> + */
> +const char *find_descendant_ref(const char *refname,
> + const struct string_list *extras,
> + const struct string_list *skip);

The documentation is is not correct. As written, the function needs not
the refname as argument but the refname followed by '/'. Without the
trailing slash, "refs/heads/foo" would be blocked by "refs/heads/foobar".

>From the point of view of simplicity, it would be nice if this function
could take a refname (without the trailing slash) as argument. But then
it would basically be forced to allocate a new string, copy refname to
it, append a '/', then free the string again when it's done.
Alternatively, it could accept its refname argument in a strbuf and
temporarily append the '/'.

But neither one of these alternatives is so elegant, so maybe it's OK if
this function is documented to take a "directory name, including the
trailing '/'" as argument and rename the argument (e.g., to "dirname").

Please also document that "skip" and "extras" can be NULL, but if not
NULL they need to be sorted lists.

> [...]

Michael

-- 
Michael Haggerty
mhag...@alum.mit.edu

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Re: [PATCH v3 37/44] refs: break out a ref conflict check

[David Turner]

On Tue, 2015-10-13 at 12:25 +0200, Michael Haggerty wrote:
> On 10/12/2015 11:51 PM, David Turner wrote:
> > Create new function verify_no_descendants, to hold one of the ref
> > conflict checks used in verify_refname_available.  Multiple backends
> > will need this function, so it goes in the common code.
> > 
> > Signed-off-by: David Turner 
> > ---
> >  refs-be-files.c | 33 -
> >  refs.c  | 22 ++
> >  refs.h  |  7 +++
> >  3 files changed, 37 insertions(+), 25 deletions(-)
> > 
> > [...]
> > diff --git a/refs.c b/refs.c
> > index 5a3125d..3ae0274 100644
> > --- a/refs.c
> > +++ b/refs.c
> > @@ -1101,6 +1101,28 @@ enum peel_status peel_object(const unsigned char 
> > *name, unsigned char *sha1)
> > return PEEL_PEELED;
> >  }
> >  
> > +const char *find_descendant_ref(const char *refname,
> > +   const struct string_list *extras,
> > +   const struct string_list *skip)
> > +{
> > +   int pos;
> > +   if (!extras)
> > +   return NULL;
> > +
> > +   /* Look for the place where "$refname/" would be inserted in extras. */
> 
> The comment above is misleading. See my note at the bottom of this email
> for an explanation.
> 
> > +   for (pos = string_list_find_insert_index(extras, refname, 0);
> > +pos < extras->nr; pos++) {
> > +   const char *extra_refname = extras->items[pos].string;
> > +
> > +   if (!starts_with(extra_refname, refname))
> > +   break;
> > +
> > +   if (!skip || !string_list_has_string(skip, extra_refname))
> > +   return extra_refname;
> > +   }
> > +   return NULL;
> > +}
> > +
> >  /* backend functions */
> >  int refs_initdb(struct strbuf *err, int shared)
> >  {
> > diff --git a/refs.h b/refs.h
> > index 3aad3b8..f8becea 100644
> > --- a/refs.h
> > +++ b/refs.h
> > @@ -637,6 +637,13 @@ int files_log_ref_write(const char *refname, const 
> > unsigned char *old_sha1,
> > const unsigned char *new_sha1, const char *msg,
> > int flags, struct strbuf *err);
> >  
> > +/*
> > + * Check for entries in extras that start with "$refname/", ignoring
> > + * those in skip. If there is such an entry, then we have a conflict.
> > + */
> > +const char *find_descendant_ref(const char *refname,
> > +   const struct string_list *extras,
> > +   const struct string_list *skip);
> 
> The documentation is is not correct. As written, the function needs not
> the refname as argument but the refname followed by '/'. Without the
> trailing slash, "refs/heads/foo" would be blocked by "refs/heads/foobar".
> 
> From the point of view of simplicity, it would be nice if this function
> could take a refname (without the trailing slash) as argument. But then
> it would basically be forced to allocate a new string, copy refname to
> it, append a '/', then free the string again when it's done.
> Alternatively, it could accept its refname argument in a strbuf and
> temporarily append the '/'.
> 
> But neither one of these alternatives is so elegant, so maybe it's OK if
> this function is documented to take a "directory name, including the
> trailing '/'" as argument and rename the argument (e.g., to "dirname").
> 
> Please also document that "skip" and "extras" can be NULL, but if not
> NULL they need to be sorted lists.

I think `extras` may not be NULL.  But I've otherwise fixed this.
Thanks.

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[PATCH v3 37/44] refs: break out a ref conflict check

[David Turner]

Create new function verify_no_descendants, to hold one of the ref
conflict checks used in verify_refname_available.  Multiple backends
will need this function, so it goes in the common code.

Signed-off-by: David Turner 
---
 refs-be-files.c | 33 -
 refs.c  | 22 ++
 refs.h  |  7 +++
 3 files changed, 37 insertions(+), 25 deletions(-)

diff --git a/refs-be-files.c b/refs-be-files.c
index 8d1ffce..dd2c42e 100644
--- a/refs-be-files.c
+++ b/refs-be-files.c
@@ -730,6 +730,7 @@ static int verify_refname_available_dir(const char *refname,
struct strbuf *err)
 {
const char *slash;
+   const char *extra_refname;
int pos;
struct strbuf dirname = STRBUF_INIT;
int ret = -1;
@@ -835,33 +836,15 @@ static int verify_refname_available_dir(const char 
*refname,
}
}
 
-   if (extras) {
-   /*
-* Check for entries in extras that start with
-* "$refname/". We do that by looking for the place
-* where "$refname/" would be inserted in extras. If
-* there is an entry at that position that starts with
-* "$refname/" and is not in skip, then we have a
-* conflict.
-*/
-   for (pos = string_list_find_insert_index(extras, dirname.buf, 
0);
-pos < extras->nr; pos++) {
-   const char *extra_refname = extras->items[pos].string;
-
-   if (!starts_with(extra_refname, dirname.buf))
-   break;
-
-   if (!skip || !string_list_has_string(skip, 
extra_refname)) {
-   strbuf_addf(err, "cannot process '%s' and '%s' 
at the same time",
-   refname, extra_refname);
-   goto cleanup;
-   }
-   }
+   extra_refname = find_descendant_ref(dirname.buf, extras, skip);
+   if (extra_refname) {
+   strbuf_addf(err,
+   "cannot process '%s' and '%s' at the same time",
+   refname, extra_refname);
+   } else {
+   ret = 0;
}
 
-   /* No conflicts were found */
-   ret = 0;
-
 cleanup:
strbuf_release();
return ret;
diff --git a/refs.c b/refs.c
index 5a3125d..3ae0274 100644
--- a/refs.c
+++ b/refs.c
@@ -1101,6 +1101,28 @@ enum peel_status peel_object(const unsigned char *name, 
unsigned char *sha1)
return PEEL_PEELED;
 }
 
+const char *find_descendant_ref(const char *refname,
+   const struct string_list *extras,
+   const struct string_list *skip)
+{
+   int pos;
+   if (!extras)
+   return NULL;
+
+   /* Look for the place where "$refname/" would be inserted in extras. */
+   for (pos = string_list_find_insert_index(extras, refname, 0);
+pos < extras->nr; pos++) {
+   const char *extra_refname = extras->items[pos].string;
+
+   if (!starts_with(extra_refname, refname))
+   break;
+
+   if (!skip || !string_list_has_string(skip, extra_refname))
+   return extra_refname;
+   }
+   return NULL;
+}
+
 /* backend functions */
 int refs_initdb(struct strbuf *err, int shared)
 {
diff --git a/refs.h b/refs.h
index 3aad3b8..f8becea 100644
--- a/refs.h
+++ b/refs.h
@@ -637,6 +637,13 @@ int files_log_ref_write(const char *refname, const 
unsigned char *old_sha1,
const unsigned char *new_sha1, const char *msg,
int flags, struct strbuf *err);
 
+/*
+ * Check for entries in extras that start with "$refname/", ignoring
+ * those in skip. If there is such an entry, then we have a conflict.
+ */
+const char *find_descendant_ref(const char *refname,
+   const struct string_list *extras,
+   const struct string_list *skip);
 
 enum expire_reflog_flags {
EXPIRE_REFLOGS_DRY_RUN = 1 << 0,
-- 
2.4.2.644.g97b850b-twtrsrc

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