[BUG, PATCH v3 0/3] Fix {blame,cat-file} --textconv for cases with symlinks

Recently I've spot a bug in git blame --textconv, which was wrongly calling pdftotext (my *.pdf conversion program) on a symlink.pdf, and I was getting something like

    $ git blame -C -C regular-file.pdf
    Error: May not be a PDF file (continuing anyway)
    Error: PDF file is damaged - attempting to reconstruct xref table...
    Error: Couldn't find trailer dictionary
    Error: Couldn't read xref table
    Warning: program returned non-zero exit code #1
    fatal: unable to read files to diff

That errors come from pdftotext run on symlink.pdf being extracted to /tmp/ with one-line plain-text content pointing to link destination.

Please apply and thanks, Kirill

v3:

 o Slightly changed patches descriptions as per comment by Matthieu, and added
   Matthieu's Reviewed-by.

v2:

 o Incorporated suggestions by Matthieu and Jeff (details in each patch)

Kirill Smelkov (3):
  tests: Prepare --textconv tests for correctly-failing conversion
    program
  blame,cat-file: Demonstrate --textconv is wrongly running converter
    on symlinks
  blame,cat-file --textconv: Don't assume mode is ``S_IFREF | 0664''

 builtin.h                        |    2 +-
 builtin/blame.c                  |   33 ++++++++++++++-------
 builtin/cat-file.c               |    2 +-
 sha1_name.c                      |    2 +
 t/t4042-diff-textconv-caching.sh |   25 ++++++++--------
 t/t8006-blame-textconv.sh        |   58 +++++++++++++++++++++++++++++++++----
 t/t8007-cat-file-textconv.sh     |   36 ++++++++++++++++++++---
 7 files changed, 121 insertions(+), 37 deletions(-)