Support specifying the user configuration with KAKOUNE_CONFIG_DIR

Fixes #3072
Closes #3081

2 files changed, 20 insertions, 8 deletions

diff --git a/doc/kak.1 b/doc/kak.1
index 9dec4890..38530979 100644
--- a/doc/kak.1
+++ b/doc/kak.1
@@ -148,10 +148,11 @@ one or more \fIfile\fRs to edit
 .PP
 At  startup, if \fB\-n\fR is not specified, Kakoune will try to source the file
 \fI../share/kak/kakrc\fR relative to the kak binary. This kak file will then
-try to recursively source any files in \fI$XDG_CONFIG_HOME/kak/autoload\fR
-(with \fI$XDG_CONFIG_HOME\fR defaulting to \fI$HOME/.config\fR, and falling back
-to \fI../share/kak/autoload\fR if that autoload directory does not exist),
-and finally \fI$XDG_CONFIG_HOME/kak/kakrc\fR.
+try to recursively source any files in \fI$KAKOUNE_CONFIG_DIR/autoload\fR
+(with \fI$KAKOUNE_CONFIG_DIR\fR defaulting to \fI$XDG_CONFIG_HOME/kak\fR
+if \fI$XDG_CONFIG_HOME\fR is set, \fI$HOME/.config/kak\fR if it is not,
+and falling back to \fI../share/kak/autoload\fR if that autoload directory
+does not exist), and finally \fI$XDG_CONFIG_HOME/kak/kakrc\fR.
 
 That leads to the following behaviour: by default, with no user autoload
 directory, the system wide autoload directory is used, once the user wants
@@ -189,6 +190,16 @@ kak \-f "ggO// kak: tabstop=8<esc>" *.c
 .RE
 .fi
 
+.SH ENVIRONMENT
+
+.TP
+.BR KAKOUNE_POSIX_SHELL
+Overrides the posix shell binary path to use for \fI%sh{...}\fR expansion.
+
+.TP
+.BR KAKOUNE_CONFIG_DIR
+Overrides the location of the directory containing kakoune user configuration.
+
 .SH FILES
 
 If not started with the \fB\-n\fR switch, Kakoune will source the \fI../share/kak/kakrc\fR file relative to the kak binary,
diff --git a/src/main.cc b/src/main.cc
index e725afc5..de2dba2d 100644
--- a/src/main.cc
+++ b/src/main.cc
@@ -123,10 +123,11 @@ String runtime_directory()
 
 String config_directory()
 {
-    StringView config_home = getenv("XDG_CONFIG_HOME");
-    if (config_home.empty())
-        return format("{}/.config/kak", homedir());
-    return format("{}/kak", config_home);
+    if (StringView kak_cfg_dir = getenv("KAKOUNE_CONFIG_DIR"); not kak_cfg_dir.empty())
+        return kak_cfg_dir.str();
+    if (StringView xdg_cfg_home = getenv("XDG_CONFIG_HOME"); not xdg_cfg_home.empty())
+        return format("{}/kak", xdg_cfg_home);
+    return format("{}/.config/kak", homedir());
 }
 
 static const EnvVarDesc builtin_env_vars[] = { {