cmake: remove obsolete version env var

The `FISH_BUILD_VERSION_FILE` variable was only read in
`doc_src/conf.py`. There, it can be replaced by the
`build_tools/git_version_gen.sh` script, which takes the version from a
file called `version` at the workspace root if one exists, and otherwise
from git. This should cover all cases where the docs are built, so there
is no need to keep using the `FISH_BUILD_VERSION_FILE` variable.

Part of #12307

cmake/Docs.cmake

@@ -24,8 +24,7 @@ endif()
 
 add_custom_target(sphinx-docs
     mkdir -p ${SPHINX_HTML_DIR}/_static/
-    COMMAND env FISH_BUILD_VERSION_FILE=${CMAKE_CURRENT_BINARY_DIR}/${FBVF}
-        PATH="${SPHINX_HTML_FISH_INDENT_PATH}:$$PATH"
+    COMMAND env PATH="${SPHINX_HTML_FISH_INDENT_PATH}:$$PATH"
         ${SPHINX_EXECUTABLE}
         -j auto
         -q -b html
@@ -34,21 +33,18 @@ add_custom_target(sphinx-docs
         "${SPHINX_SRC_DIR}"
         "${SPHINX_HTML_DIR}"
     DEPENDS
-        CHECK-FISH-BUILD-VERSION-FILE
         ${SPHINX_SRC_DIR}/fish_indent_lexer.py
         ${SPHINX_HTML_FISH_INDENT_DEP}
     COMMENT "Building HTML documentation with Sphinx")
 
 add_custom_target(sphinx-manpages
-    env FISH_BUILD_VERSION_FILE=${CMAKE_CURRENT_BINARY_DIR}/${FBVF}
-        ${SPHINX_EXECUTABLE}
+    ${SPHINX_EXECUTABLE}
         -j auto
         -q -b man
         -c "${SPHINX_SRC_DIR}"
         -d "${SPHINX_ROOT_DIR}/.doctrees-man"
         "${SPHINX_SRC_DIR}"
         "${SPHINX_MANPAGE_DIR}/man1"
-    DEPENDS CHECK-FISH-BUILD-VERSION-FILE
     COMMENT "Building man pages with Sphinx")
 
 if(NOT DEFINED WITH_DOCS) # Don't check for legacy options if the new one is defined, to help bisecting.

doc_src/conf.py

@@ -117,16 +117,10 @@ copyright = "fish-shell developers"
 author = "fish-shell developers"
 issue_url = "https://github.com/fish-shell/fish-shell/issues"
 
-# Parsing FISH-BUILD-VERSION-FILE is possible but hard to ensure that it is in the right place
-if "FISH_BUILD_VERSION_FILE" in os.environ:
-    # From Cmake
-    f = open(os.environ["FISH_BUILD_VERSION_FILE"], "r")
-    ret = f.readline().strip()
-else:
-    # From Cargo, or no build system.
-    ret = subprocess.check_output(
-        ("../build_tools/git_version_gen.sh", "--stdout"), stderr=subprocess.STDOUT
-    ).decode("utf-8")
+# From Cargo, or no build system.
+ret = subprocess.check_output(
+    ("../build_tools/git_version_gen.sh", "--stdout"), stderr=subprocess.STDOUT
+).decode("utf-8")
 
 # The full version, including alpha/beta/rc tags
 release = ret.strip().split(" ")[-1]