[Buildroot] [PATCHv2] docs/manual: using a branch name as FOO_VERSION does not work

Yann E. MORIN yann.morin.1998 at free.fr
Fri May 11 15:50:58 UTC 2018

For various reasons, we've always suggested users to avoid using a
branch as version string for their packages, because it does not work
as a they would expect:

  - it is not reproducible, because the branch may change between two
    builds that are done at different times;

  - it does not even follow the branch, as Buildroot anyway generates
    a local tarball, which it will reuse on subsequent builds.
    Furthermore, since we fetch and not pull, any existing local branch
    is not updated.

Yet, until recently, using a branch name would just work (with the
above limitations): the git tree was cloned, the branch checked out,
and the tarball created.

But with the advent of the git caching, using a branch name does not
work anymore. Indeed, we now do a git-fetch, and that does not create
local master branch. So we can't check out master, because it does not
exist locally. And for other branches, as noticed above, the local
branch does not get udpated to the remote one.

Furthermore, the local branches are only created by chance, again as a
side-effect of trying to fetch the "special refs".

So, we can't say that we reliably support the use of a branch name.

Update the manual to state that using a branch does not work. Remove
the 'stable' example, as it looked like the name of a stable branch;
instead, replace it with a version string that ressemble a tag.

Fix the layout of the manual by making the version examples an actual
bulleted list.

Note: the above is only entirely true for git. For Mercurial, CVS and
subversion, the status may be mixed, but nonetheless, using branches is
still a bad idea, if at least because it is not reproducible, and
because Buildroot does not even follow the branch. So, we do not
differentiate between the various SCMs, and just flatly state that using
a branch name is not supported.

Signed-off-by: "Yann E. MORIN" <yann.morin.1998 at free.fr>
Cc: Thomas De Schampheleire <patrickdepinguin at gmail.com>
Cc: Thomas Petazzoni <thomas.petazzoni at bootlin.com>
Cc: Maxime Hadjinlian <maxime.hadjinlian at gmail.com>
Cc: Peter Korsgaard <peter at korsgaard.com>

Changes v1 -> v2:
  - enhance commit log with additional details  (Ricardo)
  - blurb about
  - typoes in commit log  (Ricardo)
 docs/manual/adding-packages-generic.txt | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/docs/manual/adding-packages-generic.txt b/docs/manual/adding-packages-generic.txt
index 7e1f246752..8ea8ce6037 100644
--- a/docs/manual/adding-packages-generic.txt
+++ b/docs/manual/adding-packages-generic.txt
@@ -199,12 +199,12 @@ information is (assuming the package name is +libfoo+) :
 * +LIBFOO_VERSION+, mandatory, must contain the version of the
   package. Note that if +HOST_LIBFOO_VERSION+ doesn't exist, it is
   assumed to be the same as +LIBFOO_VERSION+. It can also be a
-  revision number, branch or tag for packages that are fetched
-  directly from their revision control system. +
-  Examples: +
-    +LIBFOO_VERSION = 0.1.2+ +
-    +LIBFOO_VERSION = cb9d6aa9429e838f0e54faa3d455bcbab5eef057+ +
-    +LIBFOO_VERSION = stable+
+  revision number or a tag for packages that are fetched directly
+  from their revision control system. Do not use a branch name as
+  version; it does not work. Examples:
+  ** a version for a release tarball: +LIBFOO_VERSION = 0.1.2+
+  ** a sha1 for a git tree: +LIBFOO_VERSION = cb9d6aa9429e838f0e54faa3d455bcbab5eef057+
+  ** a tag for a git tree +LIBFOO_VERSION = v0.1.2+
 * +LIBFOO_SOURCE+ may contain the name of the tarball of the package,
   which Buildroot will use to download the tarball from

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