[Bug-vc-dwim] bug#21120: vc-chlog fails if git submodules are dirty

[Assaf Gordon]

Hello,

it seems that if a project using git has a submodule that is dirty, vc-chlog 
will fail to print the information about all the files.

To reproduce:
====
   git clone git://git.sv.gnu.org/hello.git
   cd hello/
   ./bootstrap
   echo >> bootstrap.conf
   echo >> gnulib/cfg.mk
   echo >> src/hello.c
====

The diff looks like this:
===
$ git diff
diff --git a/bootstrap.conf b/bootstrap.conf
index 9e6b005..79d4c5b 100644
--- a/bootstrap.conf
+++ b/bootstrap.conf
@@ -119,3 +119,4 @@ bootstrap_epilogue()
     done
   fi
 }
+
diff --git a/gnulib b/gnulib
--- a/gnulib
+++ b/gnulib
@@ -1 +1 @@
-Subproject commit b9bfe78424b871f5b92e5ee9e7d21ef951a6801d
+Subproject commit b9bfe78424b871f5b92e5ee9e7d21ef951a6801d-dirty
diff --git a/src/hello.c b/src/hello.c
index 8e6cfbd..f0d12de 100644
--- a/src/hello.c
+++ b/src/hello.c
@@ -187,3 +187,4 @@ License GPLv3+: GNU GPL version 3 or later 
<http://gnu.org/licenses/gpl.html>\n\
 This is free software: you are free to change and redistribute it.\n\
 There is NO WARRANTY, to the extent permitted by law.\n"), COPYRIGHT_YEAR);
 }
+
===

But vc-chlog will stop after the gnulib submodule:
===
$ vc-chlog
2015-07-22  gordon  <address@hidden>

        * bootstrap.conf:
        * gnulib:
===

A bit of debugging seems to show that in 'vc-chlog', the output of 
'processed-diff()' is:
   bootstrap.conf 1 3 9 0-0-122-122
   gnulib 1 11 15 1-1-1-1
   src/hello.c 1 18 24 0-0-190-190

Then 'func_extract_identifiers()' calls 'func_apply_tmp_patch()' which runs 
'patch', and patch fails.
 
One possible work-around is to ignore submodules in 'vc-dwim' (attached patch).

Another possible thing is to make 'vc-dwim' abort if there are dirty 
submodules, on the assumption that 'vc-dwim' is meant to prevent problematic 
commits, and a dirty submodule is a hint of a potential problem.
related to this approach, there was a discussion couple of months about about 
adding a server-side git hook in savannah to prevent such commits, but it was 
decided against such forcible approach. perhaps warning about dirty submodules 
in 'vc-dwim' is more polite?
  http://lists.gnu.org/archive/html/coreutils/2015-04/msg00017.html


regards,
 - assaf

vc-dwim-ignore-git-submodules.patch
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