在Snap容器中启动非标准库路径的Tcl/Tk程序（gitk/git-gui）

问题背景 #

我开发的Git前端工具需要启动gitk和git-gui这两个Tcl/Tk程序，在常规Linux系统运行正常，但在Snap容器中出现异常。Snap容器的文件系统根路径带前缀，实际的Tcl/Tk库路径为：

/snap/multigit/x21/usr/share/tcltk/tcl8.6
/snap/multigit/x21/usr/share/tcltk/tk8.6

容器内测试过程 #

未调整环境变量时的错误 #

直接执行gitk，出现路径查找失败：

osboxes@osboxes:/snap/multigit/x21/usr/share/tcltk$ gitk
application-specific initialization failed: Can't find a usable init.tcl in the following directories: 
    /usr/share/tcltk/tcl8.6 /snap/multigit/x21/usr/lib/tcl8.6 /snap/multigit/x21/lib/tcl8.6 /snap/multigit/x21/usr/library /snap/multigit/x21/library /snap/multigit/x21/tcl8.6.12/library /snap/multigit/tcl8.6.12/library
This probably means that Tcl wasn't installed properly.
Error in startup script: can't find package Tk
    while executing
"package require Tk"
    (file "/snap/multigit/x21/usr/bin/gitk" line 10)

尝试指定TCL_LIBRARY为公共目录 #

设置环境变量指向Tcl/Tk的公共父目录：

export TCL_LIBRARY="/snap/multigit/x21/usr/share/tcltk"

再次执行gitk仍报错：

osboxes@osboxes:/snap/multigit/x21/usr/share/tcltk$ gitk
application-specific initialization failed: Can't find a usable init.tcl in the following directories: 
    /snap/multigit/x21/usr/share/tcltk /snap/multigit/x21/usr/share/tcl8.6 /usr/share/tcltk/tcl8.6 /snap/multigit/x21/usr/lib/tcl8.6 /snap/multigit/x21/lib/tcl8.6 /snap/multigit/x21/usr/library /snap/multigit/x21/library /snap/multigit/x21/tcl8.6.12/library /snap/multigit/tcl8.6.12/library
This probably means that Tcl wasn't installed properly.
Error in startup script: can't find package Tk
    while executing
"package require Tk"
    (file "/snap/multigit/x21/usr/bin/gitk" line 10)

指定TCL_LIBRARY为Tcl库目录 #

设置环境变量指向具体的Tcl库目录：

export TCL_LIBRARY="/snap/multigit/x21/usr/share/tcltk/tcl8.6"

此时gitk能启动，但提示缺少msgcat包：

osboxes@osboxes:/snap/multigit/x21/usr/share/tcltk$ gitk
Error in startup script: can't find package msgcat
    while executing
"package require msgcat"
    (file "/snap/multigit/x21/usr/bin/gitk" line 12279)

查找发现msgcat位于Tcl库的子目录中：

osboxes@osboxes:/snap/multigit/x21/usr/share/tcltk$ find . | grep msgcat 
./tcl8.6/tcl8/msgcat-1.6.1.tm

尝试传递多路径到TCL_LIBRARY #

尝试多种多路径写法（分号、冒号、逗号、空格分隔），均失败：

export TCL_LIBRARY="/snap/multigit/x21/usr/share/tcltk/tcl8.6;/snap/multigit/x21/usr/share/tcltk/tcl8.6/tcl8"
export TCL_LIBRARY="/snap/multigit/x21/usr/share/tcltk/tcl8.6:/snap/multigit/x21/usr/share/tcltk/tcl8.6/tcl8"
export TCL_LIBRARY="/snap/multigit/x21/usr/share/tcltk/tcl8.6,/snap/multigit/x21/usr/share/tcltk/tcl8.6/tcl8"
export TCL_LIBRARY="/snap/multigit/x21/usr/share/tcltk/tcl8.6  /snap/multigit/x21/usr/share/tcltk/tcl8.6/tcl8"

所有写法均触发相同的初始化错误：

osboxes@osboxes:/snap/multigit/x21/usr/share/tcltk$ gitk
application-specific initialization failed: Can't find a usable init.tcl in the following directories: 
    {/snap/multigit/x21/usr/share/tcltk/tcl8.6  /snap/multigit/x21/usr/share/tcltk/tcl8.6/tcl8} {/snap/multigit/x21/usr/share/tcltk/tcl8.6  /snap/multigit/x21/usr/share/tcltk/tcl8.6/tcl8.6} /usr/share/tcltk/tcl8.6 /snap/multigit/x21/usr/lib/tcl8.6 /snap/multigit/x21/lib/tcl8.6 /snap/multigit/x21/usr/library /snap/multigit/x21/library /snap/multigit/x21/tcl8.6.12/library /snap/multigit/tcl8.6.12/library

This probably means that Tcl wasn't installed properly.
Error in startup script: can't find package Tk
    while executing
"package require Tk"
    (file "/snap/multigit/x21/usr/bin/gitk" line 10)

求助问题 #

如何让Tcl通过TCL_LIBRARY递归查找库文件，或者如何向TCL_LIBRARY传递多个有效路径？

内容的提问来源于stack exchange，提问作者Philippe F