update_tags.sh: make UPDATED_SOURCE relative to tags file

[blueyed]

Fixes #70.

TODO:

• port it for plat/win32/update_tags.cmd

[ludovicchabant]

Hi, thanks but I don't want a dependency on Python so we'll have to find a different implementation...

When the cache dir is not set (i.e. when we store the tags file at the project root) we already run a chdir in Vim before running the script so I think making the file path relative in that same if block would solve your problem no?

[blueyed]

I am using the script itself also outside of Vim, e.g. from a Git hook - so it should be done in the script.
It could be done in shell code, too - but having it in POSIX (/bin/sh shebang) certainly does not make it easier. But I do not want to switch to using bash for the script just because of this, too.

[ZyX-I]

This is not going to work if path contains backslash, single quote or some of the control characters. Should be

A="$1" B="$2" python -c 'import os; print(os.path.relpath(os.environ["A"], os.environ["B"]))'

(you may also pass this as an argument after -c command, but this would require two imports).

[blueyed]

Good point, but we need something without Python anyway.

[ZyX-I]

I know only one way so far: ln --relative --symbolic with readlink. But this is GNU-coreutils-specific, BSD ln seems to not have this argument. I am wondering why you want exactly relative path? It seems that absolute path is easier to construct:

abspath() {(
    test "x$2" '!=' "x" && cd "$2"
    cd "$(dirname "$1")"
    printf '%s/%s\n' "$(pwd)" "$(basename "$1")"
)}

[blueyed]

I don't remember.. but it will be shorter at least.

[ludovicchabant]

I did what I said (make the file path relative in Vimscript) with commit 09fbdfc. If you run the script from a git hook you shouldn't have problems passing that path to the script in a relative way, no? (since the hook itself runs in the git repo AFAIK).