[PATCHv3 4/6] gdb/doc: also look in srcdir when running TEXI2POD

[Andrew Burgess <aburgess@redhat.com>]

In gdb/doc/Makefile.in the TEXI2POD variable is used to invoke
texi2pod.pl, which process the .texinfo files.  This also handles the
'include' directives within the .texinfo files.

Like the texi2dvi and texi2pdf tools, texi2pod.pl handles the -I flag
to add search directories for resolving 'include' directives within
.texinfo files.

When GDB runs TEXI2POD we include gdb-cfg.texi, which then includes
GDBvn.texi.

When building from a git checkout the gdb-cfg.texi files and
GDBvn.texi files will be created in the build directory, which is
where texi2pod.pl is invoked, so the files will be found just fine.

However, for a GDB release we ship gdb-cfg.texi and GDBvn.texi in the
source tree, along with the generated manual (.1 and .5) files.

So when building a release, what normally happens is that we spot that
the .1 and .5 man files are up to date, and don't run the recipe to
regenerate these files.

However, if we deliberately touch the *.texinfo files in a release
source tree, and then try to rebuild the man files, we'll get an error
like this:

  make: Entering directory '/tmp/release-build/build/gdb/doc'
    TEXI2POD gdb.1
  cannot find GDBvn.texi at ../../../gdb-16.0.50.20240529/gdb/doc/../../etc/texi2pod.pl line 251, <GEN0> line 16.
  make: *** [Makefile:664: gdb.1] Error 2
  make: Leaving directory '/tmp/release-build/build/gdb/doc'

The problem is that texi2pod.pl doesn't know to look in the source
tree for the GDBvn.texi file.

If we compare this to the recipe for creating (for example) gdb.dvi,
which uses texi2dvi, this recipe adds '-I $(srcdir)' to the texi2dvi
command line, which allows texi2dvi to find GDBvn.texi in the source
tree.

In this commit I add a similar -I option to the texi2pod.pl command
line.  After this, given a GDB release, it is possible to edit (or
just touch) the gdb.texinfo file and rebuild the man pages, the
GDBvn.texi will be picked up from the source tree.

If however a dependency for GDBvn.texi is changed in a release tree
then GDBvn.texi will be regenerated into the build directory and this
will be picked up in preference to the GDBvn.texi in the source tree,
just as you would want.
---
 gdb/doc/Makefile.in | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/gdb/doc/Makefile.in b/gdb/doc/Makefile.in
index eb800bf3848..7b7b85dae10 100644
--- a/gdb/doc/Makefile.in
+++ b/gdb/doc/Makefile.in
@@ -176,7 +176,7 @@ ANNOTATE_DOC_FILES = \
 MANCONF = -Dman
 
 TEXI2POD = perl $(srcdir)/../../etc/texi2pod.pl \
-		$(MAKEINFOFLAGS) $(MAKEINFO_EXTRA_FLAGS)
+		$(MAKEINFOFLAGS) $(MAKEINFO_EXTRA_FLAGS) -I $(srcdir)
 
 
 POD2MAN = pod2man --center="GNU Development Tools"
-- 
2.25.4