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Better experience for shallow repository #534

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Better experience for shallow repository #534

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Commits on Dec 4, 2021

  1. fix build error in a shallow-cloned source tree 

    Cloning the repository with the --depth option is useful when you do
not need the full git history, but it fails to build core/version.c

  $ git clone --depth 1 git://git.ipxe.org/ipxe.git
  $ cd ipxe/src
  $ make
   [snip]
      [VERSION] bin/version.ipxe.dsk.o
  In file included from include/ipxe/features.h:6,
                   from core/version.c:33:
  <command-line>: error: unsigned conversion from ‘int’ to ‘unsigned char’ changes value from ‘9062’ to ‘102’ [-Werror=overflow]
  include/ipxe/dhcp.h:529:58: note: in definition of macro ‘DHCP_OPTION’
    529 | #define DHCP_OPTION( ... ) VA_ARG_COUNT ( __VA_ARGS__ ), __VA_ARGS__
        |                                                          ^~~~~~~~~~~
    ...

A shallow-cloned repository may not have any tag at all, then it returns
only a commit hash.

  $ git describe --tags --always --long --abbrev=1 --match "v*"
  9062

In such a case, VERSION_MINOR becomes empty, causing the build error.

If 'git describe' does not find any tag, let the version macros fall
back to the default:

  VERSION_MAJOR   = 1
  VERSION_MINOR   = 0
  VERSION_PATCH   = 0
  EXTRAVERSION    = +

Setting sha1 to GITVERSION is still useful.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
    @masahir0y
    masahir0y committed Dec 4, 2021
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  2. take exactly 7 hex characters for GITVERSION 

    git-describe(3) says:

  --abbrev=<n>
      Instead of using the default 7 hexadecimal digits as the
      abbreviated object name, use <n> digits, or as many digits
      as needed to form a unique object name. An <n> of 0 will
      suppress long format, only showing the closest tag.

The number of "digits needed to form a unique object name" depends
on your git repository, e.g. 1) how you cloned it, 2) how many local
branches you have, etc.

In the full cloned repository, --abbrev=1 for v1.21.1 gave me 5-digits
as of writing (but it may increase in the future):

  $ git checkout v1.21.1
  $ git describe --tags --always --long --abbrev=1 --match 'v*'
  v1.21.1-0-g988d2

In the repository cloned with --depth 1000, it is 4-digits.

  $ git clone --depth 1000 git://git.ipxe.org/ipxe.git
  $ ipxe
  $ git checkout v1.21.1
  $ git describe --tags --always --long --abbrev=1 --match 'v*'
  v1.21.1-0-g988d

To make the version string deterministic, use --abbrev=32 and then
take the first 7 characters, which is reasonable for this project.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
    @masahir0y
    masahir0y committed Dec 4, 2021
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