[PATCH] submodule init: warn about falling back to a local path

[PATCH] submodule init: warn about falling back to a local path

[Stefan Beller]

When a submodule is initialized, the config variable 'submodule.<name>.url'
is set depending on the value of the same variable in the .gitmodules
file. When the URL indicates to be relative, then the url is computed
relative to its default remote. The default remote cannot be determined
accurately in all cases, such that it falls back to 'origin'.

The 'origin' remote may not exist, though. In that case we give up looking
for a suitable remote and we'll just assume it to be a local relative path.

This can be confusing to users as there is a lot of guessing involved,
which is not obvious to the user.

So in the corner case of assuming a local autoritative truth, warn the
user to lessen the confusion.

This behavior was introduced in 4d6893200 (submodule add: allow relative
repository path even when no url is set, 2011-06-06), which shared the
code with submodule-init and then ported to C in 3604242f080a (submodule:
port init from shell to C, 2016-04-15).

In case of submodule-add, this behavior makes sense in some use cases[1],
however for submodule-init there does not seem to be an immediate obvious
use case to fall back to a local submodule. However there might be, so
warn instead of die here.

[1] e.g. http://stackoverflow.com/questions/8721984/git-ignore-files-for-public-repository-but-not-for-private
"store a secret locally in a submodule, with no intention to publish it"

Reported-by: Shawn Pearce <spearce@spearce.org>
Signed-off-by: Stefan Beller <sbeller@google.com>
---
 builtin/submodule--helper.c | 8 +++-----
 1 file changed, 3 insertions(+), 5 deletions(-)

diff --git a/builtin/submodule--helper.c b/builtin/submodule--helper.c
index 899dc334e3..44c11dd91e 100644
--- a/builtin/submodule--helper.c
+++ b/builtin/submodule--helper.c
@@ -356,12 +356,10 @@ static void init_submodule(const char *path, const char *prefix, int quiet)
 			strbuf_addf(&remotesb, "remote.%s.url", remote);
 			free(remote);
 
-			if (git_config_get_string(remotesb.buf, &remoteurl))
-				/*
-				 * The repository is its own
-				 * authoritative upstream
-				 */
+			if (git_config_get_string(remotesb.buf, &remoteurl)) {
 				remoteurl = xgetcwd();
+				warning(_("could not lookup configuration '%s'. Assuming this repository is its own authoritative upstream."), remotesb.buf);
+			}
 			relurl = relative_url(remoteurl, url, NULL);
 			strbuf_release(&remotesb);
 			free(remoteurl);
-- 
2.12.0.rc1.16.ge4278d41a0.dirty

Re: [PATCH] submodule init: warn about falling back to a local path

[Philip Oakley]

From: "Stefan Beller" <sbeller@google.com>
> When a submodule is initialized, the config variable 
> 'submodule.<name>.url'
> is set depending on the value of the same variable in the .gitmodules
> file. When the URL indicates to be relative, then the url is computed
> relative to its default remote. The default remote cannot be determined
> accurately in all cases, such that it falls back to 'origin'.
>
> The 'origin' remote may not exist, though. In that case we give up looking
> for a suitable remote and we'll just assume it to be a local relative 
> path.
>
> This can be confusing to users as there is a lot of guessing involved,
> which is not obvious to the user.

Would a note in the user docs about the fallback you list above also be 
useful?

>
> So in the corner case of assuming a local autoritative truth, warn the
> user to lessen the confusion.
>
> This behavior was introduced in 4d6893200 (submodule add: allow relative
> repository path even when no url is set, 2011-06-06), which shared the
> code with submodule-init and then ported to C in 3604242f080a (submodule:
> port init from shell to C, 2016-04-15).
>
> In case of submodule-add, this behavior makes sense in some use cases[1],
> however for submodule-init there does not seem to be an immediate obvious
> use case to fall back to a local submodule. However there might be, so
> warn instead of die here.
>
> [1] e.g. 
> http://stackoverflow.com/questions/8721984/git-ignore-files-for-public-repository-but-not-for-private
> "store a secret locally in a submodule, with no intention to publish it"
>
> Reported-by: Shawn Pearce <spearce@spearce.org>
> Signed-off-by: Stefan Beller <sbeller@google.com>
> ---
> builtin/submodule--helper.c | 8 +++-----
> 1 file changed, 3 insertions(+), 5 deletions(-)
>
--
Philip 

Re: [PATCH] submodule init: warn about falling back to a local path

[Stefan Beller]

On Wed, Feb 22, 2017 at 7:01 AM, Philip Oakley <philipoakley@iee.org> wrote:
>
> Would a note in the user docs about the fallback you list above also be
> useful?

duh! yes it would! Will look at the documentation and reroll.

[PATCH] submodule init: warn about falling back to a local path

[Stefan Beller]

When a submodule is initialized, the config variable 'submodule.<name>.url'
is set depending on the value of the same variable in the .gitmodules
file. When the URL indicates to be relative, then the url is computed
relative to its default remote. The default remote cannot be determined
accurately in all cases, such that it falls back to 'origin'.

The 'origin' remote may not exist, though. In that case we give up looking
for a suitable remote and we'll just assume it to be a local relative path.

This can be confusing to users as there is a lot of guessing involved,
which is not obvious to the user.

So in the corner case of assuming a local autoritative truth, warn the
user to lessen the confusion.

This behavior was introduced in 4d6893200 (submodule add: allow relative
repository path even when no url is set, 2011-06-06), which shared the
code with submodule-init and then ported to C in 3604242f080a (submodule:
port init from shell to C, 2016-04-15).

In case of submodule-add, this behavior makes sense in some use cases[1],
however for submodule-init there does not seem to be an immediate obvious
use case to fall back to a local submodule. However there might be, so
warn instead of die here.

While adding the warning, also clarify the behavior of relative URLs in
the documentation.

[1] e.g. http://stackoverflow.com/questions/8721984/git-ignore-files-for-public-repository-but-not-for-private
"store a secret locally in a submodule, with no intention to publish it"

Reported-by: Shawn Pearce <spearce@spearce.org>
Signed-off-by: Stefan Beller <sbeller@google.com>
---
 Documentation/git-submodule.txt | 22 +++++++++++++++-------
 builtin/submodule--helper.c     |  8 +++-----
 2 files changed, 18 insertions(+), 12 deletions(-)

diff --git a/Documentation/git-submodule.txt b/Documentation/git-submodule.txt
index 8acc72ebb8..d23dee2a5b 100644
--- a/Documentation/git-submodule.txt
+++ b/Documentation/git-submodule.txt
@@ -73,13 +73,17 @@ configuration entries unless `--name` is used to specify a logical name.
 +
 <repository> is the URL of the new submodule's origin repository.
 This may be either an absolute URL, or (if it begins with ./
-or ../), the location relative to the superproject's origin
+or ../), the location relative to the superproject's default remote
 repository (Please note that to specify a repository 'foo.git'
 which is located right next to a superproject 'bar.git', you'll
 have to use '../foo.git' instead of './foo.git' - as one might expect
 when following the rules for relative URLs - because the evaluation
 of relative URLs in Git is identical to that of relative directories).
-If the superproject doesn't have an origin configured
++
+The default remote is the remote of the remote tracking branch
+of the current branch. If no such remote tracking branch exists or
+the in detached HEAD mode, "origin" is assumed to be the default remote.
+If the superproject doesn't have a default remote configured
 the superproject is its own authoritative upstream and the current
 working directory is used instead.
 +
@@ -118,18 +122,22 @@ too (and can also report changes to a submodule's work tree).
 
 init [--] [<path>...]::
 	Initialize the submodules recorded in the index (which were
-	added and committed elsewhere) by copying submodule
-	names and urls from .gitmodules to .git/config.
+	added and committed elsewhere) by copying `submodule.$name.url`
+	from .gitmodules to .git/config, resolving relative urls to be
+	relative to the default remote.
++
 	Optional <path> arguments limit which submodules will be initialized.
-	It will also copy the value of `submodule.$name.update` into
-	.git/config.
-	The key used in .git/config is `submodule.$name.url`.
+	If no path is specified all submodules are initialized.
++
+	When present, it will also copy the value of `submodule.$name.update`.
 	This command does not alter existing information in .git/config.
 	You can then customize the submodule clone URLs in .git/config
 	for your local setup and proceed to `git submodule update`;
 	you can also just use `git submodule update --init` without
 	the explicit 'init' step if you do not intend to customize
 	any submodule locations.
++
+	See the add subcommand for the defintion of default remote.
 
 deinit [-f|--force] (--all|[--] <path>...)::
 	Unregister the given submodules, i.e. remove the whole
diff --git a/builtin/submodule--helper.c b/builtin/submodule--helper.c
index 899dc334e3..44c11dd91e 100644
--- a/builtin/submodule--helper.c
+++ b/builtin/submodule--helper.c
@@ -356,12 +356,10 @@ static void init_submodule(const char *path, const char *prefix, int quiet)
 			strbuf_addf(&remotesb, "remote.%s.url", remote);
 			free(remote);
 
-			if (git_config_get_string(remotesb.buf, &remoteurl))
-				/*
-				 * The repository is its own
-				 * authoritative upstream
-				 */
+			if (git_config_get_string(remotesb.buf, &remoteurl)) {
 				remoteurl = xgetcwd();
+				warning(_("could not lookup configuration '%s'. Assuming this repository is its own authoritative upstream."), remotesb.buf);
+			}
 			relurl = relative_url(remoteurl, url, NULL);
 			strbuf_release(&remotesb);
 			free(remoteurl);
-- 
2.12.0.rc1.16.ge4278d41a0.dirty

Re: [PATCH] submodule init: warn about falling back to a local path

[Johannes Sixt]

Am 24.02.2017 um 01:17 schrieb Stefan Beller:
> --- a/Documentation/git-submodule.txt
> +++ b/Documentation/git-submodule.txt
> @@ -73,13 +73,17 @@ configuration entries unless `--name` is used to specify a logical name.
> ...
> +The default remote is the remote of the remote tracking branch
> +of the current branch. If no such remote tracking branch exists or
> +the in detached HEAD mode, "origin" is assumed to be the default remote.

The part after "or" does not quite parse.

> +If the superproject doesn't have a default remote configured
>  the superproject is its own authoritative upstream and the current
>  working directory is used instead.
>  +
> @@ -118,18 +122,22 @@ too (and can also report changes to a submodule's work tree).
>
>  init [--] [<path>...]::
>  	Initialize the submodules recorded in the index (which were
> -	added and committed elsewhere) by copying submodule
> -	names and urls from .gitmodules to .git/config.
> +	added and committed elsewhere) by copying `submodule.$name.url`
> +	from .gitmodules to .git/config, resolving relative urls to be
> +	relative to the default remote.
> ++
>  	Optional <path> arguments limit which submodules will be initialized.
> -	It will also copy the value of `submodule.$name.update` into
> -	.git/config.
> -	The key used in .git/config is `submodule.$name.url`.
> +	If no path is specified all submodules are initialized.
> ++
> +	When present, it will also copy the value of `submodule.$name.update`.
>  	This command does not alter existing information in .git/config.
>  	You can then customize the submodule clone URLs in .git/config
>  	for your local setup and proceed to `git submodule update`;
>  	you can also just use `git submodule update --init` without
>  	the explicit 'init' step if you do not intend to customize
>  	any submodule locations.
> ++
> +	See the add subcommand for the defintion of default remote.

To be rendered correctly, I think you must remove the indentation from 
continuation paragraphs.

>
>  deinit [-f|--force] (--all|[--] <path>...)::
>  	Unregister the given submodules, i.e. remove the whole
> diff --git a/builtin/submodule--helper.c b/builtin/submodule--helper.c
> index 899dc334e3..44c11dd91e 100644
> --- a/builtin/submodule--helper.c
> +++ b/builtin/submodule--helper.c
> @@ -356,12 +356,10 @@ static void init_submodule(const char *path, const char *prefix, int quiet)
>  			strbuf_addf(&remotesb, "remote.%s.url", remote);
>  			free(remote);
>
> -			if (git_config_get_string(remotesb.buf, &remoteurl))
> -				/*
> -				 * The repository is its own
> -				 * authoritative upstream
> -				 */
> +			if (git_config_get_string(remotesb.buf, &remoteurl)) {
>  				remoteurl = xgetcwd();
> +				warning(_("could not lookup configuration '%s'. Assuming this repository is its own authoritative upstream."), remotesb.buf);
> +			}

If you re-roll this patch, please place the warning before xgetcwd, 
which can potentially fail.

-- Hannes

[PATCH] submodule init: warn about falling back to a local path

[Stefan Beller]

When a submodule is initialized, the config variable 'submodule.<name>.url'
is set depending on the value of the same variable in the .gitmodules
file. When the URL indicates to be relative, then the url is computed
relative to its default remote. The default remote cannot be determined
accurately in all cases, such that it falls back to 'origin'.

The 'origin' remote may not exist, though. In that case we give up looking
for a suitable remote and we'll just assume it to be a local relative path.

This can be confusing to users as there is a lot of guessing involved,
which is not obvious to the user.

So in the corner case of assuming a local autoritative truth, warn the
user to lessen the confusion.

This behavior was introduced in 4d6893200 (submodule add: allow relative
repository path even when no url is set, 2011-06-06), which shared the
code with submodule-init and then ported to C in 3604242f080a (submodule:
port init from shell to C, 2016-04-15).

In case of submodule-add, this behavior makes sense in some use cases[1],
however for submodule-init there does not seem to be an immediate obvious
use case to fall back to a local submodule. However there might be, so
warn instead of die here.

While adding the warning, also clarify the behavior of relative URLs in
the documentation.

[1] e.g. http://stackoverflow.com/questions/8721984/git-ignore-files-for-public-repository-but-not-for-private
"store a secret locally in a submodule, with no intention to publish it"

Reported-by: Shawn Pearce <spearce@spearce.org>
Signed-off-by: Stefan Beller <sbeller@google.com>
---

* reworded sentence to not omit half of it.
* tested rendering to be correct
* warn before xgetcwd

Thanks,
Stefan

 Documentation/git-submodule.txt | 36 ++++++++++++++++++++++--------------
 builtin/submodule--helper.c     |  8 +++-----
 2 files changed, 25 insertions(+), 19 deletions(-)

diff --git a/Documentation/git-submodule.txt b/Documentation/git-submodule.txt
index 8acc72ebb8..b810d37aa2 100644
--- a/Documentation/git-submodule.txt
+++ b/Documentation/git-submodule.txt
@@ -73,13 +73,17 @@ configuration entries unless `--name` is used to specify a logical name.
 +
 <repository> is the URL of the new submodule's origin repository.
 This may be either an absolute URL, or (if it begins with ./
-or ../), the location relative to the superproject's origin
+or ../), the location relative to the superproject's default remote
 repository (Please note that to specify a repository 'foo.git'
 which is located right next to a superproject 'bar.git', you'll
 have to use '../foo.git' instead of './foo.git' - as one might expect
 when following the rules for relative URLs - because the evaluation
 of relative URLs in Git is identical to that of relative directories).
-If the superproject doesn't have an origin configured
++
+The default remote is the remote of the remote tracking branch
+of the current branch. If no such remote tracking branch exists or
+the HEAD is detached, "origin" is assumed to be the default remote.
+If the superproject doesn't have a default remote configured
 the superproject is its own authoritative upstream and the current
 working directory is used instead.
 +
@@ -118,18 +122,22 @@ too (and can also report changes to a submodule's work tree).
 
 init [--] [<path>...]::
 	Initialize the submodules recorded in the index (which were
-	added and committed elsewhere) by copying submodule
-	names and urls from .gitmodules to .git/config.
-	Optional <path> arguments limit which submodules will be initialized.
-	It will also copy the value of `submodule.$name.update` into
-	.git/config.
-	The key used in .git/config is `submodule.$name.url`.
-	This command does not alter existing information in .git/config.
-	You can then customize the submodule clone URLs in .git/config
-	for your local setup and proceed to `git submodule update`;
-	you can also just use `git submodule update --init` without
-	the explicit 'init' step if you do not intend to customize
-	any submodule locations.
+	added and committed elsewhere) by copying `submodule.$name.url`
+	from .gitmodules to .git/config, resolving relative urls to be
+	relative to the default remote.
++
+Optional <path> arguments limit which submodules will be initialized.
+If no path is specified all submodules are initialized.
++
+When present, it will also copy the value of `submodule.$name.update`.
+This command does not alter existing information in .git/config.
+You can then customize the submodule clone URLs in .git/config
+for your local setup and proceed to `git submodule update`;
+you can also just use `git submodule update --init` without
+the explicit 'init' step if you do not intend to customize
+any submodule locations.
++
+See the add subcommand for the defintion of default remote.
 
 deinit [-f|--force] (--all|[--] <path>...)::
 	Unregister the given submodules, i.e. remove the whole
diff --git a/builtin/submodule--helper.c b/builtin/submodule--helper.c
index 899dc334e3..15a5430c00 100644
--- a/builtin/submodule--helper.c
+++ b/builtin/submodule--helper.c
@@ -356,12 +356,10 @@ static void init_submodule(const char *path, const char *prefix, int quiet)
 			strbuf_addf(&remotesb, "remote.%s.url", remote);
 			free(remote);
 
-			if (git_config_get_string(remotesb.buf, &remoteurl))
-				/*
-				 * The repository is its own
-				 * authoritative upstream
-				 */
+			if (git_config_get_string(remotesb.buf, &remoteurl)) {
+				warning(_("could not lookup configuration '%s'. Assuming this repository is its own authoritative upstream."), remotesb.buf);
 				remoteurl = xgetcwd();
+			}
 			relurl = relative_url(remoteurl, url, NULL);
 			strbuf_release(&remotesb);
 			free(remoteurl);
-- 
2.12.0.rc1.16.ge4278d41a0.dirty

Re: [PATCH] submodule init: warn about falling back to a local path

[Junio C Hamano]

Stefan Beller <sbeller@google.com> writes:

> When a submodule is initialized, the config variable 'submodule.<name>.url'
> is set depending on the value of the same variable in the .gitmodules
> file. When the URL indicates to be relative, then the url is computed
> relative to its default remote. The default remote cannot be determined
> accurately in all cases, such that it falls back to 'origin'.
>
> The 'origin' remote may not exist, though. In that case we give up looking
> for a suitable remote and we'll just assume it to be a local relative path.

IOW we keep the .url to be relative, the same as the original one we
took from .gitmodules?  That sounds like a sensible thing to do and
I agree it makes sense to warn when it happens.

>  <repository> is the URL of the new submodule's origin repository.
>  This may be either an absolute URL, or (if it begins with ./
> -or ../), the location relative to the superproject's origin
> +or ../), the location relative to the superproject's default remote
>  repository (Please note that to specify a repository 'foo.git'
>  which is located right next to a superproject 'bar.git', you'll
>  have to use '../foo.git' instead of './foo.git' - as one might expect
>  when following the rules for relative URLs - because the evaluation
>  of relative URLs in Git is identical to that of relative directories).
> -If the superproject doesn't have an origin configured
> ++
> +The default remote is the remote of the remote tracking branch
> +of the current branch. If no such remote tracking branch exists or
> +the HEAD is detached, "origin" is assumed to be the default remote.
> +If the superproject doesn't have a default remote configured

OK.

> @@ -118,18 +122,22 @@ too (and can also report changes to a submodule's work tree).
>  
>  init [--] [<path>...]::
>  	Initialize the submodules recorded in the index (which were
> -	added and committed elsewhere) by copying submodule
> -	names and urls from .gitmodules to .git/config.
> -	Optional <path> arguments limit which submodules will be initialized.
> -	It will also copy the value of `submodule.$name.update` into
> -	.git/config.
> -	The key used in .git/config is `submodule.$name.url`.
> -	This command does not alter existing information in .git/config.
> -	You can then customize the submodule clone URLs in .git/config
> -	for your local setup and proceed to `git submodule update`;
> -	you can also just use `git submodule update --init` without
> -	the explicit 'init' step if you do not intend to customize
> -	any submodule locations.
> +	added and committed elsewhere) by copying `submodule.$name.url`
> +	from .gitmodules to .git/config, resolving relative urls to be
> +	relative to the default remote.

I read this as "copying..., resolving relative to the default remote
(if exists)."  A reader would wonder what happens if the default
remote does not exist---don't we want to describe what happens in
that case, like, "recording . (the current repository) as the
upstream" or something?

> ++
> +Optional <path> arguments limit which submodules will be initialized.
> +If no path is specified all submodules are initialized.

Perhaps s/ all submodules/,&/?

>  deinit [-f|--force] (--all|[--] <path>...)::
>  	Unregister the given submodules, i.e. remove the whole
> diff --git a/builtin/submodule--helper.c b/builtin/submodule--helper.c
> index 899dc334e3..15a5430c00 100644
> --- a/builtin/submodule--helper.c
> +++ b/builtin/submodule--helper.c
> @@ -356,12 +356,10 @@ static void init_submodule(const char *path, const char *prefix, int quiet)
>  			strbuf_addf(&remotesb, "remote.%s.url", remote);
>  			free(remote);
>  
> -			if (git_config_get_string(remotesb.buf, &remoteurl))
> -				/*
> -				 * The repository is its own
> -				 * authoritative upstream
> -				 */
> +			if (git_config_get_string(remotesb.buf, &remoteurl)) {
> +				warning(_("could not lookup configuration '%s'. Assuming this repository is its own authoritative upstream."), remotesb.buf);

Sounds sensible (it might be a bit too long but it should be OK).

>  				remoteurl = xgetcwd();
> +			}
>  			relurl = relative_url(remoteurl, url, NULL);
>  			strbuf_release(&remotesb);
>  			free(remoteurl);

Thanks.

Re: [PATCH] submodule init: warn about falling back to a local path

[Stefan Beller]

On Fri, Feb 24, 2017 at 12:19 PM, Junio C Hamano <gitster@pobox.com> wrote:
> Stefan Beller <sbeller@google.com> writes:
>
>> When a submodule is initialized, the config variable 'submodule.<name>.url'
>> is set depending on the value of the same variable in the .gitmodules
>> file. When the URL indicates to be relative, then the url is computed
>> relative to its default remote. The default remote cannot be determined
>> accurately in all cases, such that it falls back to 'origin'.
>>
>> The 'origin' remote may not exist, though. In that case we give up looking
>> for a suitable remote and we'll just assume it to be a local relative path.
>
> IOW we keep the .url to be relative, the same as the original one we
> took from .gitmodules?

Well that is one way to say that. Another way is:
If we cannot construct a URL based on the given relative URL, we
demote the relative URL to be a relative PATH and resolve that instead.

>  That sounds like a sensible thing to do and
> I agree it makes sense to warn when it happens.

ok.

>
>> @@ -118,18 +122,22 @@ too (and can also report changes to a submodule's work tree).
>>
>>  init [--] [<path>...]::
>>       Initialize the submodules recorded in the index (which were
>> -     added and committed elsewhere) by copying submodule
>> -     names and urls from .gitmodules to .git/config.
>> -     Optional <path> arguments limit which submodules will be initialized.
>> -     It will also copy the value of `submodule.$name.update` into
>> -     .git/config.
>> -     The key used in .git/config is `submodule.$name.url`.
>> -     This command does not alter existing information in .git/config.
>> -     You can then customize the submodule clone URLs in .git/config
>> -     for your local setup and proceed to `git submodule update`;
>> -     you can also just use `git submodule update --init` without
>> -     the explicit 'init' step if you do not intend to customize
>> -     any submodule locations.
>> +     added and committed elsewhere) by copying `submodule.$name.url`
>> +     from .gitmodules to .git/config, resolving relative urls to be
>> +     relative to the default remote.
>
> I read this as "copying..., resolving relative to the default remote
> (if exists)."  A reader would wonder what happens if the default
> remote does not exist---don't we want to describe what happens in
> that case, like, "recording . (the current repository) as the
> upstream" or something?

eh, a better approach is s/copying/<something else>/
We will resolve the relative URL no matter what. It's just that
we may end up with an absolute path instead of an absolute URL.

>
>> ++
>> +Optional <path> arguments limit which submodules will be initialized.
>> +If no path is specified all submodules are initialized.
>
> Perhaps s/ all submodules/,&/?

ok

Will reroll, once I have found a better wording.

[PATCH] submodule init: warn about falling back to a local path

[Stefan Beller]

When a submodule is initialized, the config variable 'submodule.<name>.url'
is set depending on the value of the same variable in the .gitmodules
file. When the URL indicates to be relative, then the url is computed
relative to its default remote. The default remote cannot be determined
accurately in all cases, such that it falls back to 'origin'.

The 'origin' remote may not exist, though. In that case we give up looking
for a suitable remote and we'll just assume it to be a local relative path.

This can be confusing to users as there is a lot of guessing involved,
which is not obvious to the user.

So in the corner case of assuming a local autoritative truth, warn the
user to lessen the confusion.

This behavior was introduced in 4d6893200 (submodule add: allow relative
repository path even when no url is set, 2011-06-06), which shared the
code with submodule-init and then ported to C in 3604242f080a (submodule:
port init from shell to C, 2016-04-15).

In case of submodule-add, this behavior makes sense in some use cases[1],
however for submodule-init there does not seem to be an immediate obvious
use case to fall back to a local submodule. However there might be, so
warn instead of die here.

While adding the warning, also clarify the behavior of relative URLs in
the documentation.

[1] e.g. http://stackoverflow.com/questions/8721984/git-ignore-files-for-public-repository-but-not-for-private
"store a secret locally in a submodule, with no intention to publish it"

Reported-by: Shawn Pearce <spearce@spearce.org>
Signed-off-by: Stefan Beller <sbeller@google.com>
---

> Perhaps s/ all submodules/,&/?

done

> I read this as "copying..., resolving relative to the default remote
> (if exists)."

reworded with shorter sentences:
  Initialize the submodules recorded in the index (which were
  added and committed elsewhere) by setting `submodule.$name.url`
  in .git/config. It uses the same setting from .gitmodules as
  a template. If the URL is relative, it will be resolved using
  the default remote. If there is no default remote, the current
  repository will be assumed to be upstream.
...
   next paragraph
  

 Documentation/git-submodule.txt | 38 ++++++++++++++++++++++++--------------
 builtin/submodule--helper.c     |  8 +++-----
 2 files changed, 27 insertions(+), 19 deletions(-)

diff --git a/Documentation/git-submodule.txt b/Documentation/git-submodule.txt
index 8acc72ebb8..e05d0cddef 100644
--- a/Documentation/git-submodule.txt
+++ b/Documentation/git-submodule.txt
@@ -73,13 +73,17 @@ configuration entries unless `--name` is used to specify a logical name.
 +
 <repository> is the URL of the new submodule's origin repository.
 This may be either an absolute URL, or (if it begins with ./
-or ../), the location relative to the superproject's origin
+or ../), the location relative to the superproject's default remote
 repository (Please note that to specify a repository 'foo.git'
 which is located right next to a superproject 'bar.git', you'll
 have to use '../foo.git' instead of './foo.git' - as one might expect
 when following the rules for relative URLs - because the evaluation
 of relative URLs in Git is identical to that of relative directories).
-If the superproject doesn't have an origin configured
++
+The default remote is the remote of the remote tracking branch
+of the current branch. If no such remote tracking branch exists or
+the HEAD is detached, "origin" is assumed to be the default remote.
+If the superproject doesn't have a default remote configured
 the superproject is its own authoritative upstream and the current
 working directory is used instead.
 +
@@ -118,18 +122,24 @@ too (and can also report changes to a submodule's work tree).
 
 init [--] [<path>...]::
 	Initialize the submodules recorded in the index (which were
-	added and committed elsewhere) by copying submodule
-	names and urls from .gitmodules to .git/config.
-	Optional <path> arguments limit which submodules will be initialized.
-	It will also copy the value of `submodule.$name.update` into
-	.git/config.
-	The key used in .git/config is `submodule.$name.url`.
-	This command does not alter existing information in .git/config.
-	You can then customize the submodule clone URLs in .git/config
-	for your local setup and proceed to `git submodule update`;
-	you can also just use `git submodule update --init` without
-	the explicit 'init' step if you do not intend to customize
-	any submodule locations.
+	added and committed elsewhere) by setting `submodule.$name.url`
+	in .git/config. It uses the same setting from .gitmodules as
+	a template. If the URL is relative, it will be resolved using
+	the default remote. If there is no default remote, the current
+	repository will be assumed to be upstream.
++
+Optional <path> arguments limit which submodules will be initialized.
+If no path is specified, all submodules are initialized.
++
+When present, it will also copy the value of `submodule.$name.update`.
+This command does not alter existing information in .git/config.
+You can then customize the submodule clone URLs in .git/config
+for your local setup and proceed to `git submodule update`;
+you can also just use `git submodule update --init` without
+the explicit 'init' step if you do not intend to customize
+any submodule locations.
++
+See the add subcommand for the defintion of default remote.
 
 deinit [-f|--force] (--all|[--] <path>...)::
 	Unregister the given submodules, i.e. remove the whole
diff --git a/builtin/submodule--helper.c b/builtin/submodule--helper.c
index 899dc334e3..15a5430c00 100644
--- a/builtin/submodule--helper.c
+++ b/builtin/submodule--helper.c
@@ -356,12 +356,10 @@ static void init_submodule(const char *path, const char *prefix, int quiet)
 			strbuf_addf(&remotesb, "remote.%s.url", remote);
 			free(remote);
 
-			if (git_config_get_string(remotesb.buf, &remoteurl))
-				/*
-				 * The repository is its own
-				 * authoritative upstream
-				 */
+			if (git_config_get_string(remotesb.buf, &remoteurl)) {
+				warning(_("could not lookup configuration '%s'. Assuming this repository is its own authoritative upstream."), remotesb.buf);
 				remoteurl = xgetcwd();
+			}
 			relurl = relative_url(remoteurl, url, NULL);
 			strbuf_release(&remotesb);
 			free(remoteurl);
-- 
2.12.0.rc1.16.ge4278d41a0.dirty